Presenting MVPWM-102: A cheap motor controller tester anybody can make or buy

[asid61]

Original thread: http://www.chiefdelphi.com/forums/sh...d.php?t=147470

MVPWM-102 is a FRC motor controller tester similar to the AM Thrifty Throttle, featuring a 0-100% knob-adjusted forward and reverse and powered by Micro USB (android phone charger cable) or direct 5v power.

Due to fabrication limitations, I cannot implement the Talon SRX power in this revision (although I'm looking into alternative ways to do it).

Boards are $4.82 each to make not including the Talon SRX header (that makes it $5.59) or shipping. Please answer the poll on what you would pay for a product like this. I'm not aiming to make money, but I do want to be able to offer this to as many teams as I can. With that in mind, I'll be releasing the design files for both a surface-mount and a through-hole version (which is slightly more expensive, around $7 not including shipping) once I test to see if the Talon SRX header can be used. PM me if you would like the current design files.

Nerd facts: pulse high time tolerances are +/- 2us on average when the potentiometer is held still, about a 0.4% power variation, with a range of 700-2300us (slightly larger than the normal 1000-2000 range, but this is because of potentiometer limitations). Much better than I expected.

You can see a video of it outputing pulses here: https://youtu.be/rlQgoI_rx1o
The numbers on the screen are in microseconds, and change as I turn the potentiometer up and down.


Please reply below if you have any comments or reasons as to why you would or would not use this.

[Michael Hill]

I think a good in-between spot would be to sell it as a soldering kit. However, if you do that, it may be better to switch things to through hole (though SMD isn't hard, people, for some reason, think it is). If you wanted to sell it as a product, people expect a somewhat decent molded case if they're going to be using it seriously. Nobody wants to hold a bare PCB and turn a pot with no knobs, so that can drive the price up quite a bit.

[Foster]

I have and use a similar device made by a mentor on 1640. It's mounted on a 9 volt battery so it's self contained. I use it all the time to test VEX motors.

[teslalab2]

If you need production, I would love to parter! I work at a circuit board shop, and I also moonlight my own little circuit board shop.

[asid61]

Originally Posted by Michael Hill

I think a good in-between spot would be to sell it as a soldering kit. However, if you do that, it may be better to switch things to through hole (though SMD isn't hard, people, for some reason, think it is). If you wanted to sell it as a product, people expect a somewhat decent molded case if they're going to be using it seriously. Nobody wants to hold a bare PCB and turn a pot with no knobs, so that can drive the price up quite a bit.

Good point. I did get a quote for injection moulding custom cases, and to say it was expensive would be and understatement. I will definitely make something that can be 3D printed, but unless there's a cheap way to make these cases otherwise I'll stick to that. Shapeways and places like it can sell you 3D printed things anyway. Currently the case should cost around $6 if you were to order it.

As far as SMD soldering by hand goes, I avoid it as much as I can. Sometimes I'm forced to fix a part on a PCB, but depending on the package size it can really screw me up. 1208's don't usually pose a problem, but most of my work is in 0803 which takes a lot out of me.

Originally Posted by teslalab2

If you need production, I would love to parter! I work at a circuit board shop, and I also moonlight my own little circuit board shop.

Wonderful, I'll get in contact with you soon about this. I use OSHPark right now, and the turnaround times are a little too long sometimes.

Originally Posted by Foster

I have and use a similar device made by a mentor on 1640. It's mounted on a 9 volt battery so it's self contained. I use it all the time to test VEX motors.

That's a clever way to do it too. A team member of mine is making a battery pack PCB (we'll be soldering that up tonight) so if it works that would let me package this even nicer.

[teslalab2]

Do you want RoHS, or is tin/lead fine? I'm not sure if they still are,(but I know they used to be) FRC components are RoHS compliant by exemption.

[asid61]

Originally Posted by teslalab2

Do you want RoHS, or is tin/lead fine? I'm not sure if they still are,(but I know they used to be) FRC components are RoHS compliant by exemption.

I've been using tin/lead so far, but in case repairs need to be done I'm thinking about moving to load-free. I'm not sure yet, because I need to wait a few weeks for my new solder paste to come in to see if it works.
The lower melting point of tin/lead makes it easier for home production, especially because of the easily burned leds.

[teslalab2]

I can do RoHS, I can run them through our reflow oven,

edit: sorry we should be discussing this in PM

[asid61]

All the design files are up here.
MVPWM-103 is the through-hole version. Be warned though; it has no case so you'll have to design your own.

You can also purchase one of the ones I have here:
http://www.ebay.com/itm/121980834159...84.m1555.l2649
I currently have 5 in stock, but if I get more requests (PM me) I'll try and make some more.