Archive for November, 2014

 

RageBridge: The Next Generation

Nov 20, 2014 in Motor Controllers

[David Attenborough's voice]

It’s autumn at Big Chuck’s Robot Warehouse & Auto Body Center.

As the cold descends over New England, the supply of Mountain Dew and burritos becomes scarce…. and we see the Charles is busily preparing for his winter hibernation.

Deep inside his expertly crafted nest of meticulously hand-picked post-industrial waste, we see him studiously lining his abode with layers… of warm, insulating motor controllers.

The Charles will get his nutrients from these motor controllers for the rest of the winter.

He will periodically set them aflame, taking in both their radiant heat… and exacting sustenance from the magic smoke.

[end David Attenborough's voice].

Anyways, what? I have no clue how it happened, but the entire first run of RageBridges is sold out! I am retaining a few units for legacy and warranty fulfillment, but other than that… It’s gone! I never actually expected this to be the case, by the way – RageBridge 1 was more of a crapshoot than I care to admit. I wouldn’t say it was pushed out the door, but I was definitely not confident about it.

However, it has proven to be a solid performer, and I have only ever gotten a handful of units back for failure analysis. That means there are several dozen healthy and working Rages in the wild. DOZEN!

I never said I was Foxconn.

The success of Generation 1 means it’s time to roll out the changes I’ve wanted to make since Generation 1, since even if I am involved something that’s in production, I still start thinking about version 2 before the version 1 is fully out the door. From the tales of experiences of Rage users, there is really not too much to change. However, I think there’s two big threads of “customer wishes”:

  • First, that dual power input setup is actually really tacky. I did originally design Rage to just drop into the wiring harness for two Victor 883s, and it just stayed that way up to “Ship It!” time. There was no good rhyme nor reason for making the power inputs on two sides of the board.
  • Wiring the two halves of the controller together into one more epic one. Hypothetically, Rage can drive up to 90 amps continously and 180 amps max current limit (or even more if you shut off the current limit!)
  • I’ve gotten a handful of reports that the board is spotty in functionality above ~33 volts. I highly suspect this is related to the inductor still being marginal in value, which was an issue I fought on the original board revision before it started working. The symptoms are the same – the regulator resets. I’m not sure why the original test units didn’t do this, but may it has to do with aging of the components? Hell if I know. However, at least I know how to fix it.

So, to the physical form factor of the board, I’ll have to do a better job at component verification, and play with the layouts some. Past that, in terms of part selection, there are some major changes I want to experiment with.

RageBridge 1, like many of my past motor controller experiments, uses several discrete half-bridge drivers instead of more integrated chips. It was great for learning layout and how these things work, but arranging 4 of them on a board is tedious and takes up more space than it needs. Their drive strength is also more suited for larger controllers, so I’ll definitely come back to them in the future. For months, I’ve been scoping out the market of integrated H-bridge gate drive chips which will let me wrap the functionality up into one chip (or at most two chips). I’m willing to try a few different H-bridge drivers, on different board revisions, if that’s what it takes, but I think many of the market options are equivalently functional.

I settled on the Allegro A3941K, which offered a good combination of reasonably easy to use package – TSSOP is my baseline for “pain in the ass electronic part packages I never want to deal with – drive strength (current), and lack of other fancy things like current sense resistors, since I’m still keeping the Hall Effect current sensors this time around. The thing that sold me on it was the retainment of the “PWM + Direction” input topology. While it actually has two inputs “PWMH” and “PWML”, one of those inputs can be held low and the other provided the PWM duty cycle to effect synchronous rectification if the “SR” mode, which stands for… guess what, synchronous rectification, is enabled. Then, the PHASE pin is basically the “direction”. This is the same effect that I had to add a 74LS08 logic chip to RageBridge 1 to achieve, since the IR21844s are only half-bridge chips and so the “direction” output is actually four selecting pins.

Next, it’s time to catch up with the latest in distressingly current-dense power MOSFETs. I’ve been drooling at the newest Infineon HSOF package units, like the IPT007N06. It’s so very beautiful and double-side heat sink-able….

Also, expensive. The competitor I selected against it is the IRFS7530, which has all the keywords I’m looking for in its applications description (“Brushed DC motor! Brushless motors! Battery powered! Synchronous rectification! Half bridges, full bridges, and onion-ring power supplies!) so I assume IR made it just for me.  Plus, even though D2PAK-7 is a bit of a weird package, it’s not nearly as proprietary as Infineon’s HSOF right now. The switching characteristics, namely the gate charge, aren’t any worse (…not are they better) than the IRFS3006 units on RageBridge 1. However, in the end, it doesn’t even matter, as Infineon and IR will soon be the same. Geez, way to make me switch to Fairchild and NXP, guys.

I’m also making an effort to transition to all SMD parts this time to lower assembly cost and streamline the process. This includes the big electrolytic bus capacitors. I went on a capacitor shopping spree prior to starting board layout, too, and realized that they pretty much don’t make better caps than what I’m already using, at least in terms of my size constraints and high voltage demands – it’s a whole ‘nother world in low voltage land.

With no further changes planned except those parts, I started creating new devices definitions in Eagle and playing with the major part layout. Power board design is as much about layout as anything, and having the Big Power in locations easy to join with huge traces and power planes is critical.

One of the candidate layouts. This one has the advantage of keeping both the big power and ground planes in the center. Check out the big Panasonic J package 16mm electrolytic capacitor profiles there – each one, based on the one I specified, is 1000uF. That’s actually a healthy 25% increase from RageBridge 1, though it’s still not to my liking…

An alternative layout with three of those caps. Now I’m happier, but sadly I’m much less enamored with the layout in general. Looking ahead a little, the right side of the board will be difficult to route in terms of getting the current sense signals and rightmost two gates through.

Sadly, three-across on the Panasonic caps juts way out of the 2″ board width. I’m trying to keep to the dimensions of Ragebridge 1 so transitioning users will not have to make much of a change in mounting facilities… myself included.

Let’s start playing with this layout for now. I’ve added candidates for input and output pins and drawn in some preliminary power planes.

The wavy header layout to the left is courtesy of Sparkfun. I’ve found their wavy-header hole footprint to be very useful, since it holds the headers in place as you’re trying to solder one pin down. You’d think I was about to slaughter them by the way mine try to wiggle out of the holes.

RageBridge 2 will ship with headers in the kit, but they will not be assembled. This cuts down on the thru-hole processing time and cost. The single-line layout will also benefit those who are still into soldering cables in place.

I’ve gotten a little ahead here, so let me explain. First, I’ve fleshed out the power plane routing more. Next, and probably more importantly, I already found ways to break out both the gate drive and current sense lines using both the top and bottom of the board, in the alleyway between the MOSFETs’ drain tabs and source legs. This actually means everything else will be easy! I have also put down the logic power regulator, this time actually following the advice of the LM2594HVM datasheet for one-layer layout.

I’m slowly growing the schematic as the major power routing occurs, so the jumble of parts on the left side is growing.

With all the passives and accessory parts loaded in… Well, at least there is physical space for everything, so that’s a good sign. In keeping with Rage tradition (and to keep fabrication easy), I’m putting all components on the top side.

One of the challenges in routing ICs with many required peripheral passive parts is you can get almost to the end and discover the rest is actually impossible. Hence, the starting configuration is important. The patterns that look the best might not be the best placement. In this trial layout, I’ve put all the gate drive resistors and bootstrap capacitors off to one side, and the logic side passives on the other. It seems promising!

Trying to play a game of snake…

There’s always that one trace you forgot about. At least this one wasn’t bad!

After getting pretty far into it, I decided to start over with the chip in a different orientation. I’m used to routing using SOIC packages and 1206 passives, where I can plop a via down and change layers whenever I want. Here, in the TSSOP package, the center pad really prevents me from doing so. I’m tempted to stray from the manufacturer’s recommended land size so I can squeeze some vias in the gap between the pins and the pad.

This new orientation ended up working out much better. However, it meant that I had to move the mounting hole closer to the left edge as a compromise. That’s fine, since this Rage version cannot share the same heat sink design anyway.

After another few evenings of playing the game, this is pretty much it. It might look daunting, but the rest of it actually went quite smoothly due to the severely reduced discrete passives count. The only reason I was able to devote far more space on this board for FETs and capacitors (the meat and potatoes of a motor controller, I might add) was because of the new gate drive ICs.

We’ll see if that comes back to bite me.

The little cheeky label in the middle refers to the fact that the top power plane has to neck down to about 0.35″ wide to clear the set of TVS diodes next to it. This means the area is kind of marginal for the current levels I want to push through the left set of FETs. I said this was a revision 1 board… To try and mitigate the trace detonation circumstances, that area (and other similar areas) is getting a stop-mask rectangle (pictured) and likely also a rectangle of solder paste deposited for some metallic reinforcement in the area. Worst case, I will have to commission copper ‘trace boosters’ like a lot of motor controllers have.

With some minor adjustments and board art, this is it.

Wait…

After letting this design sit out of sight for a day or two, I came back to it to add a 5V rail TVS diode and to move a few traces to be less twisty and convoluted. Now we’re ready to send out…

Check out the extra “combine” option – this is directly in response to Consumer Demand™, for people who want to run a single larger motor. RageBridge v1 is technically capable of this, as both halves are driven off the same hardware timer, but the firmware was never updated to fuse the two current sensor readings and modulate the PWM as one.

RageBridge2 revision 1 should get back to me next week.

brushless rage

Uh oh…

Something that has been eating at me for a long time is I’ve technically never made a functional brushless motor controller.

Okay, to clarify, I meant “to my liking”. 6.131-troller (Face Vector Modulation) worked just fine, cementing my love of hardware and hatred of programming and software. Next, Melontroller2 did work in RazEr Rev for several months before I swapped it out. But it was very unfinished; the firmware was left in a crude state and I never went back to change it. After that, all of my controllers began suffering from the Great Bypass Capacitance Drought of 2011-2012 before I discovered the issue with Ragebridge the original.  TinyTroller, the last brushless I attempted, ended pretty much in miserable, abject failure.

Perhaps it’s time to try again. Like what motivated me to build RageBridge v1, I find myself often disappointed by the small brushless controller market. The physically small ones (Hobbyking et. al, model controllers) are bare-bones and lack features like torque (current) control and Hall sensor inputs (or even Analog inputs). The good vehicle ones tend to be very bulky (like Kelly KBS controllers) or functional but extremely power limited (Jasontrollers/Wangtrollers). Furthermore, the Kelly controllers seem to have a control discontinuity in regenerative braking mode, which manifests itself as the vehicle suddenly jerking.

Granted, Alien Power controllers do exist, but I haven’t personally used one to know what they’re made of. Anyone know more about them and if they have a good reliability track record?

Brushless Rage will therefore be my redemption experiment, and maybe a future product down the line. For now, the specifications I’d like to hit include:

  • Sensored to start with. Both idiomatically, for simplicity in development, and literally: One thing I really like about the Jasontrollers is the use of Hall sensors only at low speeds, where they make sense. At high speeds, fixed Hall sensors introduce problems in phase lag. In reversing scenarios, they have a pretty large hysteresis band.
  • HV inputs – up to 60v is my preference, since I like running high voltage and lower currents. 17-60v (nominal ratings being 24-48v) is a common input voltage band.
  • 50 to 100 amps, much like Rage, since it will be fairly similar in size and device usage.
  • Relatively simple – Kelly controllers are set up for several different kinds of throttle and brake inputs and have features for more complete vehicles, such as contactor drivers and reversing beepers and whatnot. Jasontrollers have cruise control. I’d like to have at most 1 throttle input, 1 brake analog input, one switch (e.g. ‘reverse’), a blinky LED, and a…
  • Small number of operating modes. Conventional “one throttle, one brake” with reversing switch; One-throttle-only (drag braking, non-variable braking or just complete coasting), and one-input forward and reverse (continuous control variable, like for vehicles under closed loop control). These are the modes I see most often in small project vehicles.
  • High-resolution torque control. It’s fairly easy to sense current every PWM cycle and manage it from the reading. This is not quite the same as RB’s current limiting, which does not occur synchronously with PWM.
  • Sinewave output. This one is a bit of a stretch goal, but I would like to make a sine output version. The interesting thing is, regular “brushless motor” driving (block commutation) almost requires a different architecture in code than a sine wave interpolator. It may actually be tacky to be able to switch from one to the other. Small sinewave controllers are starting to make inroads into e-bikes: I know of some that do, but they apparently suffer from slow maximum speed.
  • “Training” mode, which is featured on most Chinese e-bike controllers now. Spin the motor up open-loop (or tell the user to give it a whirl), record Hall sensor transitions, apply to your state transition table. This is definitely another stretch goal, but I really want to give this a stab.

First, though, is getting a stable hardware base for development.

Component choice-wise, this controller is a bit beyond the capabilities of the ATMega328 I am fond of for DC RageBridge.The chief reasons are lack of timer compare outputs (for PWM generation), and the killer, a very slow ADC. I’m going to move up one tax bracket to the ATMega32U4, the current chip of the Arduino Leonardo, because it actually does have a “PWM6″ output mode where it will generate three sets of complementary PWMs, all in hardware. This is common in new and motor control optimized microcontrollers, but I’m all giddy and stuff since it means I will not have to bother with external hardware to generate complementary PWM. The ADC is also faster – still quite slow by modern micro standards, but it’s workable. I calculated the (more or less) exact times needed to perform the analog read operations I needed to do per PWM cycle, and that result was what told me that 328s were hopeless, the 32u4 would be a logical step up, and that everyone uses ARM Cortex chips for a reason.

I also spent quite a few off-cycles perusing Allegro’s selection of 3-phase motor drivers. They come in all sorts of sizes and features for many different industries – some are clearly designed for automotive fans and blowers, for instance, and others for servo drives… I’m currently fond of the A4910, which is basically three half-bridge drivers and current sense amplifiers put into a box. TI has some very feature-packed chips in the form of the DRV8301 and its related parts, but in talking with Shane (who literally does this for a living now, not just figuratively any more…), I think they’re a bit beyond the requirements of this project right now, and could be facing End-of-Life in the near future.

Here is a “parts splattering” with one proposed layout of the components. The bolt pattern and size for Brushless Rage (name to be determined – suggest ‘em in the comment box) is the same right now as for DC RageBridge2, but may not remain such if I find that another configuration is better suited to the task.

I suppose the “minimum viable product” of this thing is “Kelly KBS destroyer”.

One example implementation of the mode switches might be:

  • Neither jumper set: thr1 controls current up to imax, thr2 controls current down to imin (variable braking, negative current), rev controls… well, reverse. thr1 and thr2 both at minimum would just be 0 current (coasting).
  • Jumper mode1 set: thr1 controls current up to imax, no thr1 means a fixed drag brake where the imin potentiometer is interpreted as a percentage of imax.
  • Jumper mode2 set: thr1 controls current symmetrically between imax and -imax, and reversing is handled automatically (One-input torque control mode)
  • Jumper mode 1 and 2 both set: thr1 controls speed as hard as it can, with Vcc/2 as a center voltage (zero), using imax and imin as ‘acceleration limits’ only (One-input speed control mode with torque ceiling, kind of like how DC Rage is set up)

There’s a long way to getting this board better defined and routed. For instance, I might just go totally discrete with the gate drive (back to good ol’ half bridge drivers) and use my favorite Hall-effect current sensors instead of current sense resistors and amplifiers. I will have to decide how to balance “new things” with debuggability – the best case for which is only changing 1 major variable at a time.

Rage onwards!

Some Random Little Things Updates! Caddiebike, RUSTY MEMORY Part III, and Inexpensive Chinese LED Lighting

Nov 02, 2014 in caddiebike, mikuvan

Here at Big Chuck’s Robot Warehouse & Auto Body Center, the fall semester is generally the quiet one where I actually, you know, get things done. I’m not herding go-karts during this time, unlike the spring and summer, so it’s shop facility upgrades and working on stuff at a less frantic pre-competition pace. Like last year, there’s also a section of the popular “How to Make [A Mess Out Of] (Almost) Anything” class running in the IDC fab shops, and I run orientations and trainings on our equipment for those students and more. In fact, life is so chill right now that I haven’t even touched Chibi-Mikuvan since Miku Expo. That’s how bad it is.

Of course, this just means “big van work”, among other things. Here’s a general recap of the past month, or thereabouts.

Caddie-bike

Also known as “that huge e-bike thing”… or “the battleship”, this thing was part of the inaugural cruft run, the first of many, that a running big-Mikuvan has enabled. It’s a Wavecrest Tidalforce iO cruiser bike, with a step-through frame. This thing is massive – it weighs something like 65 pounds in stock configuration, and its soft and boat-like handling earned it the nicknames shown. It’s been hanging out in the shop for nearly the past year in a quasi-operational state.

With the advent of another promising winter, I’ve decided to ‘resto-mod’ it into something usable. Melonscooter, in all its incarnations, just does not do snow at all. The fat scooter tires means you float above the snow and can’t get either traction or stability, and both wheels gradually turn into solid balls of snow. On the other hand, bikes do somewhat better, especially road bikes with thin profile tires, since they ‘cut through’ the snow – the phenomenon is something I observed very clearly watching people try to commute during winter, and borrowing a bike or two. You’re also higher off the ground in a bike, so the black slush that the snow inevitably becomes after 24 hours stays a little farther away.

To get the bike to a functional state, I decided to ditch the front hub battery like many who inherit them. There’s a small community of Wavecrest enthusiasts who have documented mods and changes to make. In particular, I’ve been in contact with Ambrose of ebikerider about the nuances of using the bike with an aftermarket battery.

First mission was to get a new front rim, since the battery-laden front rim was being removed. I rolled it over to the bike shop for a quick appraisal and parts recommendation. Cambridge Bicycle and MITERS go way back, so I usually patronize them when I can.

They also get to put up with a slew of student questions along the theme of “How can I use this on a go-kart?” at the end of each semester from me, so I also feel bad if I don’t use their business for a legitimate purpose.

Notice the the added cargo box and bag on the back. This was where I was going to put the new battery pack; specifically, the battery will go into the center cavity, leaving the upper cavity above it and the side bags free for actually carrying stuff. All of these bags ‘telescope’ a little, so it’s a fair amount of enclosed space.

Observe, enough lithium to level a small city block.

I decided to dig through the lipo nuclear arsenal to assemble a pack. To my delight, these four 4.5Ah 10S lithium polymer packs fit perfectly, four across, in the center of the bike bag. So that was a quick decision.

These are actually the batteries from the very first generation of tinykart before Shane switched to A123 cells. They have been sitting in various rooms for a while, so the first order of business is to fully charge and balance them both. I borrowed a TP1430C charger from Peter while I purchased one and it was on the way.

Surprisingly, they were in good health and all reached 4.2 volts a cell without incident. LiPo batteries like this tend to be a little more fragile because of their soft shell.

To join the packs in parallel, I had to make another Adapter Which Should Not Be Made, a 5-to-1 Deans adapter using 8mm bullet connectors as the wire-joining socket. I used the Big Weller with the 1/2″ diameter tip for this join-five-12-gauge-wires-at-once job. To prevent errant shorting when plugging in more batteries, each of the male Deans connector ends is shrouded in loosely-shrunk heat shrink tubing.

The other end of the adapter goes to a 45A Anderson PowerPole connector which is used throughout the bike.

The final outfit, with a new wide 26″ front rim. I also replaced the back-curving ‘cruiser’ style handlebars with straight bars that I could stand using. I’m not sure why the cruiser style bars are popular, but my wrists clearly were installed in the wrong orientation for me to use them comfortably. The LED cluster a cheap “56 LED” (That’s the only model name I can find for it) bike light I bought long ago for Melonscooter 1 whose mount I lost, but that was resolved with a 3D printed part.

…and that’s it! It hasn’t been hotmodded to hit 65mph (yet), nor can it go from Boston to New York (yet). I’ve put about 30 to 35 miles on it, on purpose, to test out the speed and range. With the lithium pack, I empirically obtained a range of 25 miles before the motor controller’s own low voltage protection kicked in. This was without me helping it much – if I put some work into it, I’m sure the range will be much greater.

Caddiebike is named such in homage to the floaty ride characteristics of old American ‘land yacht’ luxury cars, since it (still) weighs over 50 pounds and has very soft shock absorbers.

Operation: RUSTY MEMORY Part III

Van bodywork begets more van bodywork. The skills I had to learn and practice on big van work contributed to my ability to tackle Chibi-Mikuvan’s body shell, and the improvement in those skills I got from Chibi-Mikuvan is applied back to big-Mikuvan. I’m trapped in an infinite van loop.

Once again, the onset of cold weather is the impetus for fall-season bodywork. There are still a few problem rust spots that I haven’t gotten to, such as what I consider to be the ‘end boss’ area, the boarding steps, which have holes on both sides. However, for now, I have the area shielded from most water intrusion, so it hasn’t gotten worse.

Last month, I wanted to repaint some more of the very problematic left side. For some reason, the left side of this thing is way more scratched and dented. In particular, the left rear corner had been deteriorating for some time:

I originally wanted to sand down this area a little and just perform a simple repaint, but of course, due to the effects of Famous Last Van Words, there is no such thing as “just [verb] a simple [noun]“. By the time you see the rust bubble, it means it’s too late. The lower corner of the wheelwell is pretty well disintegrated, but I declared it “out of scope” for the day and just proceeded with repainting the dent at the top, which seems like somebody sideswiped a solid object very slowly.

Here’s the area cleaned up a little. The bottom corner has now been “scab picked” so the extent of the hole is visible.

Early October is the last time it’s warm enough to paint outdoors. Even so, I made sure to bring a heat lamp out and point it at the job as I applied more coats.

An area at the front was also repaired during this same session, since just because they write “AUTOMOTIVE” on a can of paint, does not make it fuel-resistant. The occasional fuel pump spill in that area has eaten the clear and color coat a little.

I left the area around the hole unpainted and marinating in “rust converter” spray for the next week or so while I waited on a good opening to bust into the FSAE and Solar Car team shop, where the auto lift is. It is often joked that I will eventually turn the whole thing into a composite-bodied solar car.

Here’s the hole after some more ‘scab picking’. The idea is to trim the area clean with a Dremel, cutting wheel, and abrasive grinding bits, then add several layers of fiberglass cloth, then smooth to shape.

From the inside, here’s a view of where the metal has degraded into holes. This part will be cleaned and trimmed also. In fact, since this is not on a very highly visible part of the vehicle, I am actually just amputating the entirety of the lower inside corner there, where the “bite mark” is taken out, instead of trying to reshape it.

Everywhere there is rust, there is a small rust demon that must be exorcised.

In the middle of the hole-bridging process. My standard so far has been 3 layers of glass, which I surmise makes the region actually more rigid than the rest of the thing. I don’t like to half-ass repairs: if I do something, it’s full-ass, but still ass.

After the resin sets, it’s time to build up the corner with Bondo a bit. I still hate Bondo, but it’s so useful as a material for this kind of work. It’s almost like they designed it for this purpose or something.

There’s two stages of Bondo-work that I seem to do now; first, is “glob on with reckless abandon”, roughly sculpting said reckless abandon to shape, then finely sanding to a visual contour.

A 2nd round then goes on to fill hole and low spots, and that’s when I put away the power sander and resort to hand sandpaper-pushing, since the power sander would be too aggressive at that point.

Here’s the result of “pass 1, fine sculpt”. There’s still some uneven spots to be filled in.

After pass 2, it’s time for priming and painting. I’m not a classic car restoration neckbeard, so the details are not perfect – the oblique lighting in fact reveals the small errors in the contour I left.

I am a adherent of the 5-foot school of cosplay costume creation and automotive bodywork: If it looks fine from like 5 feet away under daylight, and functions fine, then I’m cool with it.

In fact, the only way someone would see this if they were running their hands along it. And if someone is feeling up the underside of my van, then I might need to have a few words with ‘em.

The few little black spots are accidental spillovers of the thick black underbody coating paint that I thoroughly smothered the obverse of this area in. The little bit of “orange peel” effect reflected by the room lights was taken care of also.

Letting everything sit overnight under the influence of a large halogen work lamp, here’s the result the next day!

There’s only two major rust removal project left on this thing – the area just behind the front left wheel, which had the most extensive large-area damage, and of course the step holes.

Inexpensive Chinese LED Lighting

Ah, another Inexpensive Chinese name, unfortunately not nearly as cool as ICBM (Inexpensive Chinese Brushless Motor), which I’m glad has spread beyond my immediate influence.

Under the category of “I have nothing left to fix, so I have to start making problems” van work is replacing all the auxiliary lighting with LEDs. I originally conceived this as a step on the way to electrification in order to reduce the power consumption of lighting and other vehicle systems. So perhaps, it’s just keeping the dream alive. Based on the prevalence of 5W “T10″ type bulbs, I calculated that I could reduce the power draw of the auxiliary lighting by 66%.

The plan is to replace all the dashboard warning and info icon lights, interior lights, and all the exterior market lights, reverse lights, brake lights, but not turn signals. Why? Because the flasher unit is an older mechanical type, so it counts on the high current draw of filament light bulbs to function. It’s also deep in the dashboard area. No, it’s not located on the fuse panel like a reasonable engineer would do so. This is a job for another day.

I gradually forgot about this as other van shenanigans took over, but DealExtreme made the critical mistake of showing me a promotion for automotive LED replacement bulbs a few weeks ago and made me remember again. The pain is real.

This is what happened. This isn’t the entire haul, either – I also haunted eBay and Amazon simultaneously like when hunting for any other Chinese-supplied resource, and got a few better deals and other form factors from there.

In the fashion I typically preach when it comes to procuring Chinese parts for peoples’ projects, I “shotgun selected” these bulbs. Meaning, I bought a whole bunch of variations and small specification differences to cross correlate which ones are clones and which actually perform up to their nameplate. The fact that you have to do this is a pretty important consequence of buying cheap Chinese parts that many engineers and makers fall victim to, which some of my students get a taste for in 2.00gokart.

I chose to go “middle of the road” sorted by price. One of my own rules of thumb when it comes to Chinese sourcing is to never buy the cheapest thing unless you’re out to use it for something other than its stated purpose; and the most expensive thing is basically like buying from a “real” name brand or established vendor, so you might as well just do that for customer support and service.

 

The dashboard job was actually quite quick, since I only had to remove the instrument panel and not the whole dashboard. The backlighting was made of three T10/W5W lamps, which I replaced with “1 watt” LED clusters, and the small icons were all T5 miniature bulbs with the exception of the fuel level indicator, which was weird (I later found out it was called a “T4.7″, but I am not going back in for just 1 light right now).

I chose these for all T10 size lamps, so I have a few different colors – white, warm white, red, and amber. I am not a fan of “warm white” in general, even in indoor lighting, and getting rid of the awkwardly yellow “white” lights was part of the reasoning behind this changeover, but just in case WW looked less out of place in one application, I wanted to have it on hand.

For the T5 miniature bulbs, I got these super cute one-LED things in several different colors. As it turns out, the dash icons themselves were colored filters, so I couldn’t use all my fancy colors like cool white and blue and Miku aqua and the like – they just looked “off”, or even greenish, which I would not want as a “You have no oil pressure.” warning light… So they became all red, with the exception of the turn signal indicators, which I used the green ones on, and even switching those out had a visible effect on the flashing frequency of the signals (hence why the external bulbs have to stay Analog until I dig out the flasher unit)

I also found out that the high beam indicator appears to be wired directly to a relay, or is otherwise strongly influencing the circuit, because I totally put a LED in that location and then had no high beams. Analog electrical systems…

In classic “Unintentional Van Consequences” fashion, lowering the power draw of the front electrical harness drastically meant the voltage rose much higher…. and blew out some of the tiny little bulbs living in the switches and buttons. Now, these things I am certain are weird and proprietary.

I had to repair these by soldering in small green LEDs and 1/8W resistors. The photo shows an exaggeration of the lighting gradient in the buttons – they’re quite even in color when you look at them.

All of the exterior marker lights are replaced with LED equivalents in the proper colors.

All interior lights were of the 29mm “Festoon” type, but there were few choices in that size, so I decided to go to the 31mm Festoon and bend the contacts out a little. They’ll live.

The “12-SMD” replacement seems to be the most popular in this size, so I got a handful of these in red and white.

The thing I’m most proud of, though, are these “buttheadlights”. I went all-out and wondered what would happen if I replaced the incandescent bulb with something of the same wattage – 10 watts. The answer is buttheadlights.

The reversing and brake lights are type 1156 and 1157 respectively, and I got these for the reversing lights. I actually am now having second thoughts about replacing the brake lights with their red equivalents, because these things are so bright it’s borderline dangerous to someone behind me. I think I’ll plunder some 5W or smaller ones in a similar form factor later.

During my shopping for all of these lights, I discovered they currently do make LED sealed-beam-replacement headlights. I’m not entirely convinced they work well, though, and they’re also still very expensive. Here’s another vendor I was looking at, and these appear to be the “Chinese copy-and-paste philosophy” off-brand kinds.

LED Lessons

There are a number of caveats for those who want to go LED that I discovered in this adventure, and they surround the nameplate rating and physical form factor.

First, shady Chinese parts being shady (but well-lit?) Chinese parts, some of the LED chips seem to be very overdriven or overrated. Specifically, amber/orange and red LEDs have more of a problem with this in my collection than the white, blue, green, etc. This is probably due to the much lower foward voltage of the semiconductor used to make red LEDs (yellow, orange, and so on are based off red LEDs), and the current-limiting resistor being improperly selected. This is hard to fix if the resistor isn’t out in the open, and almost makes switching not worthwhile because of the re-engineering needed

The symptom is lots of heat generation and the LED dims after a while, and some of the wire bonds might even fail and cause one of the dies to go out. The small single-chip T5 lights and the small 1156 sized amber lights I bought have this problem, the T10 size and the “buttheadlight” 9W 1156 lamps did not. This seems to be hit or miss, and so I’d caution people away from buying on the cheap unless you actually do love messing with these things like I do.

Second, you might notice that a lot of these bulbs are way bigger than their equivalent incandescent packages. This is an issue for marker lights, interior lights, etc. where the bezel isn’t very large. At least, you could hold up your bulb to an image of the product and see roughly how much larger it is. Otherwise, you could have to sacrifice brightness for fit purposes.

I got lucky in that the only bulb I bought which didn’t fit directly was the orange front side marker lights, and that was a length discrepancy small enough that I just cut half of the contacts on the circuit board off. But I can’t even imagine how some of those ridiculous corn cob shaped LED wads even begin to fit in their specified form factors. That product right there is my favorite example of “Chinese copy and paste design philosopy” – take what works, then CTRL-C & CTRL-V.

I’m not sure how much more buying the cheap LEDs on heat sinks will help – heat sinks only prolong the time until thermal stress and failure if they’re enclosed in a bubble like most automotive lighting is. That’s why even most home lighting LED products caution against using it in enclosed or recessed light fixtures, because LEDs still generate lots of heat – they’re often cited as “3 times more efficient” than incandescent bulbs or something, but that’s because their luminous efficiency is like 10% instead of 3%. The rest of the 90% is still heat.

I’d say the bottom line here is, I like my glowy cool-white Tron lights enough to shotgun the market and mess with products; if you just want straight up replacements with no hassle, I’m actually not sure what to tell you…