Author Topic: Curtis 1208C Component Question  (Read 2393 times)

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RndmGuy06

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Curtis 1208C Component Question
« on: September 02, 2016, 09:10:09 AM »
All,

I have a Curtis 1208C controller and the TH1 location the component is missing. I jumped it and everything works great on a bench but once I apply a load there is little power. I believe a capacitor should go here. Does anyone know what size or why a cap is needed?

Specific photo of missing component located here.http://s1124.photobucket.com/user/RndmGuy06/media/Mobile%20Uploads/Curtis%201208c/C7986941-5780-4282-A823-FADB9D1AEA40.jpg.html

Other pictures located in this album. http://s1124.photobucket.com/user/RndmGuy06/library/Mobile%20Uploads/Curtis%201208c

Thank you everyone in advance!
-Erik

RndmGuy06

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Re: Curtis 1208C Component Question
« Reply #1 on: September 02, 2016, 09:15:20 AM »
Long Story about how I ended up where I am today with my power wheels project.

About 2 years ago a buddy heard me talking about building a power wheels. Said I've got something that might work. I ended up with a motor, transaxle, controller that didn't work and a bunch of cut off control wires. I got it working on a bench by seeing a gap at TH1. The rigid leads to something we're still sticking out of the board like a capacitor or something shot off. I checked voltage and jumped it. It worked on my bench and I thought it was fixed. Life happened and we moved.

Fast forward 2 years to last month. I was given an old pedal go kart and thought there's my frame. Wired it all up. Tried using my RC grade 500w 18v power supply to drive tethered to an extension cord. Assumed throttle cutoff was happening due to less than 24 volt supply. Randomly would stop like an intermittent connection somewhere. Grabbed 2 3s Lipo batteries from my fpv quad. Still am getting the random drop out where it just goes back to neutral, but using the Lipo was able to haul me 250lb plus my 4 yr old 40 lbs around our cull de sac. Including a pretty steep incline up the road via the sidewalk. I drove it through the grass and it would slow slightly and power through and up and over the height variance of the driveway and grass. It gave me a glimmer of what this would be like, the best power wheels ever! :) and totally worth my efforts to make this work right.

Grabbed two 12v 8.5 ah ups batteries I had, and it can't put the amps down. Still have some random drop to neutral like a glitch in the 5k ohm throttle. But I just adjust the pot back to 2.5 ohm, it's a wig wag throttle, and start moving again. I can't find a short yet, but if I let the entire pot and wires rotate in my hand, kind of like dropping the pot wire assembly and letting it hang, it drops to neutral.

Bought a volt and amp meter, installed yesterday. Only showed up to 5 amps when applying the parking brake. Previously on my bench using my multi meter I was showing up to 3 amp but that was unloaded with me holding the wires to the leads and I assumed poor connections were limiting my current.

Today two things should arrive. 5 volt foot throttle to try out a different control method and prove out my potentiometer. And a cheap Amazon 40 amp pwm dc controller to troubleshoot my motor. Don't want to use this due to lack of soft start and auto parking brake.

If you made it this far thank you for reading all of this.

mab

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Re: Curtis 1208C Component Question
« Reply #2 on: September 02, 2016, 01:45:36 PM »
my 1st thought was TH1 might be thyristor - but there are only two 'legs' so maybe a thermistor? If so it might be for an over-temperature shutdown, but I'm guessing it was not implemented at the factory so not worth trying to fit it now. Unless you think the controller may be overheating I doubt it will make a difference anyway.

RndmGuy06

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Re: Curtis 1208C Component Question
« Reply #3 on: September 02, 2016, 01:59:29 PM »
my 1st thought was TH1 might be thyristor - but there are only two 'legs' so maybe a thermistor? If so it might be for an over-temperature shutdown, but I'm guessing it was not implemented at the factory so not worth trying to fit it now. Unless you think the controller may be overheating I doubt it will make a difference anyway.

I have thought about a thermistor. It shouldn't be getting too hot to start throttling back my current after a min. When I get home I will touch the wire under power to gauge the temperature.

Any thoughts on why I'd only be getting 5 amps when the controller came with a 50 amp breaker?

mab

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Re: Curtis 1208C Component Question
« Reply #4 on: September 02, 2016, 03:15:46 PM »
This is a pure guesswork, but if you replaced TH1 with the jumper, then it may be that TH1 was a negative temp coeficient thermistor (resistance goes down as temp goes up) which derates the controller as the temperature goes up. by replacing with a straight wire you're making the controller 'think' it's very hot, so it's limiting the current.

trouble is, guessing what sort of NTC thermisitor is needed.

RndmGuy06

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Re: Curtis 1208C Component Question
« Reply #5 on: September 02, 2016, 06:09:38 PM »
This is a pure guesswork, but if you replaced TH1 with the jumper, then it may be that TH1 was a negative temp coeficient thermistor (resistance goes down as temp goes up) which derates the controller as the temperature goes up. by replacing with a straight wire you're making the controller 'think' it's very hot, so it's limiting the current.

trouble is, guessing what sort of NTC thermisitor is needed.

That makes the most sense. Thank you for the suggestion. I have an extra 5k pot. Sounds like a good place to start.

I'll try it in the morning.