Paul & Sabrina's cheap DIY 144v motor controller

[xtian999]

Another Q: Where is a good place to tap the power for a fan? I am going to put the fan on the outside of the case and let it vent through the sides (for Texas temps). Don't want to disrupt any delicate circuits.

[adamj12b]

Originally Posted by xtian999

Thank you. To be sure, I am talking about adding ten equal length wires and just leaving the gate resistors on the power side of the mounting board instead of pushing them through the holes. So, when I lift the controller board up away from the power section to fix something, all the resistor leads do not have to flex. I'm just looking down the road a bit to make things more service-friendly.

Yes, That will work fine. Just get as close to the same length as you can.

-Adam

[adamj12b]

Originally Posted by xtian999

Another Q: Where is a good place to tap the power for a fan? I am going to put the fan on the outside of the case and let it vent through the sides (for Texas temps). Don't want to disrupt any delicate circuits.

Is the fan 12V like a PC fan? If it is, Just connect it up to the 12V input to the controller. That would be your best and easiest bet. I would say crimp the leads of it into the crimps with the 5 pin main connector.

-Adam

[xtian999]

Yes, it is like a pc fan, only much bigger. About 6" across and 2" thick. I will splice in a plug for it and see what happens. If it causes the controller to fry, then we will know that it was a big fan of irony.

[adamj12b]

You will want to run it parallel with the controller, not inline with the + side if thats what you mean.


+ of the fan connects to the + of the controller input and - of the fan connects to the - of the controller input. This way, the fan will only run when the controller has power because it will be getting its power from the same battery through the same switch.

-Adam

[xtian999]

I hadn't meant that, but I see what you mean. In looking at possible ways to improve cooling, I noticed that the bent portion of the case could provide additional heat sinking if it had some thermal paste where it joins the plate. Also, better air flow inside if the mounting board were perforated. Any objections to swapping some pre-perfed material here?

[xtian999]

Still looking at my kit and wondering. Why put the brain inside with the mosfets at all? It could be separated by a cable and thus free from the radio frequencies and heat. Keep a couple extras around for field servicing. Use the mounting plate inside to put a fan right over the mosfets.

Does anyone ever mount capacitors or mosfets on plugs so they can be replaced when they blow?

Do I need 12 batteries to get 144 volts, or can fewer be amplified to drive the controller?

[Tweety]

Originally Posted by xtian999

Still looking at my kit and wondering. Why put the brain inside with the mosfets at all? It could be separated by a cable and thus free from the radio frequencies and heat. Keep a couple extras around for field servicing. Use the mounting plate inside to put a fan right over the mosfets.

Does anyone ever mount capacitors or mosfets on plugs so they can be replaced when they blow?

Do I need 12 batteries to get 144 volts, or can fewer be amplified to drive the controller?

The reason you solder Mosfet's and Cap's are simple... You create large losses with a "plug in"... And it's not the right place to introduce losses...

The reason for the control board near the powerstage is the same... Make the PWM lead to long (where you plan to put "flexible leads") and you get losses, resulting in the whole thing going bonkers...

Agreed you could make the controller better separated in terms of HF shielding... But You really, really want the controller card close to the powerstage... A cable longer than adding a few inches is not something I'd recommend...

And the last question... Again... Say it with me... "Losses!"... Yeah you can amplify things... But you loose more in the process than you can ever gain...

"Thinking outside the box" is a good thing... But sometimes things are done in a certain way because all others failed...

[adamj12b]

The only way to effectly get the control out of power area is to use a high speed interface between the power stage and the logic stage. But even doing this, you would still have electronics inside the power stage.

-Adam

[xtian999]

You mean the others who failed to think outside the box? Lol.
I can overcome losses with better materials. What I cannot overcome is a burnt out, soldered in capacitor on the side of the road. If I can use screw mount caps and modular control units, I can get home without a tow truck. That is a gain worth asking about.