If I remember correctly from your other thread, you are a team of high school students?

These days I would expect a high school team to have a member who can use BASIC Stamps or Arduinos etc, or access to a person who does use them.

That might be a good option for the "brains" part of the controller.

 

You could replace everything to the left of the driver, but would need to add a small voltage regulator and of course the PIC. You would need to buy a programmer(probably about $20) and learn how to program the PIC.

If its not too much to ask, would it be possible for you to create another schematic of the circuitry with the new PIC idea? Since we are very new at this we like to have something to constantly reference to.

 

I'm not a PIC guy, but maybe Mr. RB can make you a schematic. If not I'll wing it.

 

That would be much appreciated!!

 

https://docs.google.com/document/d/1yXWsOUt8VTMAsPRseaRB5aIUtwZRiPrcbAiwAG700bs/edit?usp=sharing

Here is our purchase list. Is everything here acceptable to create this motor controller?

 

Unless you have someone who understands micros or someone jumps in to help, I don't think that is the way to go. But having said that, here is a site for you to read about how to do it. Pay careful attention to the micro code involved.

Here is a single chip PWM controller that might be easier to implement.
http://www.supertex.com/pdf/datasheets/HV7100.pdf
http://picprojects.org.uk/projects/ppc/index.htm

 

Re the schematic, David Cook's excellent RobotRoom website has this one;

Basically you use a NFET instead of the NPN transistor, but they both do the same thing. The FET is able to handle more current, which you need. I would also change the 1k resistor to a 100 ohm resistor.

The left side of the resistor connects directly to the microcontroller or arduino output pin, and they share a common ground.

If you look back at what I said in post #5 in this thread, it's a great idea to google for "PWM motor controller kit schematic" and you will find a lot of simple circuits you can use.

This project will require YOU doing some of the work.

 

NCC

Here is an update.

 

Bug with low voltage detect.

 

Hey guys this is an update.... Not everything seems to be working, but its a work in progress

 

Here are some more pictures

 

Hi NCC,

You may not be able to run it on the strip board because of the high current of the motor, but we can worry about that later. I can't remember if you have access to a scope or not. If you do it's great if not we can take some voltage measurements with a meter. So, for now take the motor out of the circuit and lets replace it with an LED and resistor. Just a little 20 ma LED and lets say a 3k resistor. The resistor should be at least 1 watt so maybe 3 1k 1/2 watt ones in series would work. So it would be anode of the led to +48 resistor(s) to the cathode and the other end of the resistors to the FET. Then just try it, it might work. If not lets measure the output of U4 with the throttle at both extremes. Then the output of U2, the +12 and the FET gate.

 

We do not have access to a scope, but we do have a multimeter and we spent a lot of time taking large measurements. After we replaced the motor with a string of 12v LEDs. When we turned the battery on, the LEDs came on. We first tested the inductors voltage and on average, we got about 10V. After we did some tinkering we were able to get the 12+ nominal voltage. (Or sometimes a random 34.4+) Also, it doesn't seem to matter which way the U4 is turned the readings seem to stay the same. We are reading about 1.5V-2.0V off the U4.

Feeling very hopeful we tried to attach the motor and it is just pulling to much power to run...

What should we try next?

 

It looks like the IC in the second picture is not wired correctly. I don't see anything on pin 3 - it should be +12. And pin 12 looks like it goes to 12 volts and not ground? I'm guessing you used 2 339 ics? Maybe some picture from a little more above?
Don't hook the motor to it. You will need heatsinks for the FET and diode and I think the sense resistor is too small. The little contacts on the board won't hold up to the high current once it starts running so that would be real bad. Just use the leds for now then we can build the power stuff on a breadboard.

 

The IC's are correctly wired. They may not have been in those first pictures, but they are now. I am not sure what the sense resistor is, could you explain it to us? Our board doesn't seem to have a problem handing the current, but I definetly not as experienced as you are. Is there a way to test our board to make sure it can handle the high current?

 

It's really hard to follow everything from the pictures, so lets try to narrow it down a little bit. Lets name the ic by the potentiometer UP and the other one UO so we can locate them. With no motor connected lets take some measurements with the voltmeter. Black lead to ground in all cases.
UP - 3
UO - 3
UP-14
UP-7 with the pot in both extremes.
UP-1 with pot in both extremes.
UO - 10
UO-11
UO-9
FET gate

You will need to build the high power stuff on another breadboard using wires. 40 amps is a lot of current - just look at the size of the wires for your motor. Besides the power components will need a heat sink like this:

http://www.mouser.com/ProductDetail/Aavid-Thermalloy/504222B00000G/?qs=XF/z8BtdrptQos6B0WOfeg==

The sense resistor is the .01 ohm resistor that looks like a squashed piece of wire. It won't do 40 amps either so we need one like this.
http://www.vishay.com/docs/50050/lto50.pdf

Once we get it debugged we can worry about those. Sorry I forgot to tell you the wattage of the sense resistor.

So lets get some voltage readings and see what's cookin.

 

Disclaimer: There was quite a bit of variance in these Voltages, while testing the LEDs flickered brighter and dimmer. We tried to measure when the LEDs were brighter (9.8V from inductor), but that may not be true 100% of the time.

UP-3 31.5 V
UO-3 12V
UP-14 31.5
UP-7 21; 28
UP-1 10;30
UO-8 10
UP-9 10.4
UO-7 25
UO-6 0
FET 10.1

Any suggestions on breadboards that can handle the current?

 

Good.
UP -3 and 14 should be 12 volts so it would seem it is somehow connected to your high voltage (48v) supply. This may have damaged the IC. - probably did.
UO7 and 6 should have been UO-11 and 9. I'll see if I can tell from the picture, but you may see the problem with UP right away.

 

We can probably use what is called a strip board. You can find them on ebay. The use wire for the high current portion.

 

UO-9 10.3
UO-11 00.00
As you can see in this picture there is nothing attached to UO-11, so thankfully we got no voltage.

Also, there is no external damage on the IC, but we will trade it out for one of our back-ups the next time we test this controller.

Another question, it doesn't seem to matter what position our potentiometer is in, it doesn't seem to do anything to the lights. Is this just because we still are debugging these circuits or is there something else the matter??

Once again thank you for your help!!!!!!!!!!!!!!!!!!!!!!!!!!