# Curtis 1205-111



## Greenflight (Sep 13, 2007)

If you replaced any of the MOSFET drivers it's possible to do something like that... I know a lot of driver ICs are offered in two versions, usually differentiated by like one number in the part number. One version is just a standard version, the other is reversed- high on the input means low on the output. That would reverse the duty cycle.


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## Tesseract (Sep 27, 2008)

I didn't think the Curtis' even used gate driver ICs? Otmar of Cafe Electric fame reverse-engineered the circuit for the Curtis 1221 here:

http://cafeelectric.com/curtis/

Nothing more exotic than LM339 comparators and LM324 op-amps in that thing.


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## piotrsko (Dec 9, 2007)

how about switching the two end pot wires, but not the center (wiper) wire?

should give you a decent "reversing" effect

you may have to go poking about in the pot box to find the variable resistor. if it is a 2 wire system, just move the end wire to the other end, but always leave the wiper lead alone. (this is the one that has a variable resistance to it when it moves)


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## honn1002 (Nov 26, 2008)

piotrsko said:


> how about switching the two end pot wires, but not the center (wiper) wire?
> 
> should give you a decent "reversing" effect
> 
> you may have to go poking about in the pot box to find the variable resistor. if it is a 2 wire system, just move the end wire to the other end, but always leave the wiper lead alone. (this is the one that has a variable resistance to it when it moves)


Model 1205-111 is a 2 wire pot throttle, 5.5K-0. It has pot lo and pot hi, no wiper. It doesn't give the reverse effect when you switch the two wires. First I thought it was, but not.


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## jsodemann (Oct 19, 2008)

Thanks for all of the suggestions. I've done some more investigating and found this unit was actually designed this way. Idon't know how common it is, but when I compared the schematic to the 1205-111 I found that the "low" input is wired to +V instead of being grounded as in a mormal Curtis. There was alos some slight differences on the "high" input side. The PC Board was set up for both so I did some hacking and got it working the "mormal" way, but now instead of going to 0% duty cycle when contact is lost to the pot it goes to 100%. I guess I have some more hacking to do. Oh, another thing of interest, this controller is running at 1KHz, which is about 10 to 15 times lower than normal.


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## trkbilder (Feb 27, 2011)

Sounds like a set up for a fork lift!


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