View Single Post
Old 04-22-2012, 11:23 PM
Turion's Avatar
Turion Turion is offline
Platinum Member
Join Date: Nov 2009
Posts: 2,620
Originally Posted by citfta View Post
Hi guys,

I have finally gotten some time to work on this again. I have gotten a mosfet switching circuit to work on this. I have the motor connected the same as we have been doing and the mosfets connected across batt 3 to vary the current through the motor. It works very well with my little radio shack motor. It also will control my scooter motor although it will get pretty warm depending on the duty cycle. I have attached a schematic of the mosfet circuit. Thanks to Vissie for allowing me to modify his circuit and share it with the rest of you.

While I was working on this I had a scope connected to my 2 good batts to look at the spikes coming back to them. I discovered something that seems pretty strange. I only had the motor connected with the mosfet circuit as a load on batt 3. I have a switch in line between the motor and batt 1 positive. When I turn that switch off I still get spikes back to the good batts until the motor comes to a stop. There shouldn't be any way for the spikes to get back to the batts because the circuit is open. I checked this several times and they were always there until the motor stopped. I am using shielded scope leads so I don't think they were picking up the spikes and especially since the ground lead was still connected to - connection on the battery. Strange?

I haven't forgotten about your circuit, or about what you said about the spikes hitting the primaries AFTER the circuit was turned off until the motor stopped running, even though there was an open circuit. It's one of those things I have circled in red in my notes! LOL I haven't replicated your circuit, mostly because I couldn't make out the part numbers an things on it, and when I blew up the picture you posted, it was too fuzzy to read. I have to look at those things 50 times before I can figure out how to build them, because electronics is definitely NOT my strength! Neither is spelling! So I kinda blew it off, figuring if it worked out for you THEN I'd give it a shot. Wrong attitude, I know!

"I aim to misbehave" Malcolm Reynolds
"Try Not! Do or do not. There is no 'Try' ". Yoda

Last edited by Turion; 04-22-2012 at 11:36 PM.
Reply With Quote