Paul & Sabrina's cheap DIY 144v motor controller

[Roger Heuckeroth]

ga2500ev

Building reliable electronics is a mater of engineering the circuitry properly. Once the design is complete, I have no doubt that Paul's 500A, 144V controller will be quite reliable.

On the other hand there will be arcing and sparking in this mechanical design. The contact surfaces will wear out. I don't want to discourage you from trying this approach, but the result will be an inherently less reliable than a properly engineered solid state design.

Don't get me wrong, there are cases where a mechanical solution is more reliable than an electrical solution. BMW has been talking for years about steer by wire being the future. No thank you! Give me a nice reliable mechanical link to steer the car. I don't se any advantage to steer by wire. Automakers may like the concept because it makes it simpler to go from left side to right side drive. But steering is a case where there is very little mechanical wear. Over time the steering knuckles may need to be replaced, however, its a proven long term solution.

I just don't believe the PWM controller can be made more reliable of less expensively with a mechanical substitution. But don't let me stop you from proving me wrong.

[MazdaMatt]

Can we move this discussion to a new thread? Maybe a moderator could disect these posts out to a "mechanical controller" thread.

[68 TT]

Originally Posted by MPaulHolmes

For the car I'm estimating:

12"x8"x0.25" (bottom of controller)
12"x5"x0.25" (top. It will need room for heatsink, but I don't have that yet.)
12"x4"x0.25" (side)
12"x4"x0.25" (side)
8"x4"x0.5" (back)
8"x4"x0.5" (front)

I can cut it later once I get my mill.

I was thinking of drilling all the sides into the front and back, so I put 0.5" thick for front and back, to give more room for screws to go in. Do you think 0.25" would be OK for putting small screws in? If so, back and front could be 0.25" as well.

Forgive the late post but I just found this site and thread. I worked for 13 years in the aircraft repair / fabrication industry so I have a little experience with what you are working on as far as the heat sink and enclosure go.

If you just double up the 1/4" material at the fastener locations and glue it together you can get the thicker material only where needed and keep the weight and material cost down. Lexan is pretty pricey in thicker chunks. 1/2" is more than twice the cost of 1/4".

You may be able to even use 1/8" material with reinforced corner joints in some of the areas like the top and sides.

It is also possible to glue threaded inserts into the clear sheet material to give it some strength. They make threaded inserts that go in like rivets too that would be quick and easy to install with no adhesive required.

You can also heat the material and bend it into the shape you desire to eliminate many of the corner joints.

A local place for you to get the stuff in small pieces is onlinemetals.com

They sell small quantities of metals and plastics that may get you what you need.

Hope this helps,
Mike

[bennelson]

Hey Paul!

Have fun showing off your car tomorrow!

[MPaulHolmes]

Thanks, Ben! Man, it has been an adventure getting that ghetto version drivable for tomorrow. I got shocked for the first time. Don't tell my wife, she's right next to me, but isn't looking at what I'm typing. Must act casual...

The momentary on pre-charge switch had failed ON during that last little pre-charge resistor mishap. So, when I hooked up the leads to B+ and B-, they were secretly charging, because the switch was ON (EVEN THOUGH IT WASN'T "ON"). So I touched B- and M- at the same time, and it hurt.

There is something wrong with the overcurrent shutdown on the old control board. I just have to stay under the limit! or else the control;ler gets turned off and stays off.

[Electric Frenzy]

sorry to ask this but I can't read through 112 pages for two simple questions:

1. When will this be ready (rough estimate)
and
2. At what cost? (rough estimate).


I'd like to support the members of this forum in my build if possible.

[NiHaoMike]

Have you thought about adding a neon bulb with a series resistor as a voltage present indicator?

[nubie]

When we get it all finalized maybe a custom case of metal would be best?

This outfit even has a free CAD tool called Protocase Designer:

Protocase Incorporated - Custom Electronic Enclosures for Engineers and Designers

I'm not sure if it would be a good idea for a couple more revisions, but it might be good if there is enough demand.

I am a big fan of a nice metal case. (also, you could put a big fan in a nice metal case, oh no, it is pun time!)


It looks like silkscreen and colors are options, but totally unnecessary for people just into functionality.

[bennelson]

Another fun place to look for case design would be a web page like INSTRUCTABLES. Lots of people on there make little project cases from all sorts of things like yogurt containers, Altoids tins, etc.

Maybe people could start looking for a container that's pretty close to the right size, but is "garbage" - leftover from something else.

Who knows? Maybe a 12-pack of widgets come in a case that would be perfect to build a controller in?


Hey Paul, getting zapped is NOT fun! You know whats even NOT Funner? 144 volts!!!! Oh, well, I will not do that again! (Until I get another experimental 144v controller shipped to me again....)

[MPaulHolmes]

It's coming soonish, Ben! Want to hear good news? Here's the plan for testing the control board: THE pro is doing the gerber layout, and then I'll send it to the PCB fab house to get 3 made, then I'm ordering the parts for 3 control boards, and I'm shipping all that stuff to him, and he works at a professional lab with digital storage oscilloscopes, precision voltage and current sources, and all sorts of stuff so he can simulate all the necessary signals. He's going to assemble the first board, do all the testing and fine tuning, figuring out which resistor or capacitor values or whatever need to change, and then use the remaining 2 boards to improve on the first. He's even doing up a Bill of Materials! Ya, it's pretty dang awesome... It will be a couple weeks, since I need to wait for the old Sylvan Check. booya! They overpaid me by about $10, so they had to send it back to the check making place. haha!

Awesome ideas, Nubie and Ben! The case of the missing case! Well, not missing case, but case that doesn't exist yet. I think it's illegal if it's not metal, due to EMI interference. ATM machine. Hi HI How How Are Are You You.