# 6-12v curtis throttle?



## domosher (Jul 10, 2011)

If you need help with this control I could repair it to the normal configuration


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## tenthousandclowns (Jun 21, 2012)

I was assuming it would be easier to make the throttle than to open up the controller. Any ideas on price to switch it back?


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## major (Apr 4, 2008)

tenthousandclowns said:


> I got a curtis 1221 controller on ebay.. and the curtis repair people (FSIP) say it is custom made for Taylor Dunn and has a 6.3V (no throttle) to 10.6V (full throttle) range.
> 
> Has anybody managed to find or make a throttle like that?


Hi 10,000,

Something smells fishy. Can you post full part # and photo?

major


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## tenthousandclowns (Jun 21, 2012)

Here is a photo of the one that is on ebay now... mine is the same but the SS# is one lower.

When I asked FSIP, the authorized curtis repair people, they said:

"Your controller was made specifically for Taylor Dunn and has a 6.3V (no throttle) to 10.6V (full throttle) range."

They said this is not a throttle they have available..


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## major (Apr 4, 2008)

What do the signal connectors look like? 2-wire or 3-wire for throttle?


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## tenthousandclowns (Jun 21, 2012)

One wire, at the #2 position. The voltage is against the B-, so not isolated from the high voltage circuit.

I was thinking of adding the appropriate potentiometer to an isolated 12v dc-dc supply from the accessory 12v.

The guy from FSIP suggested "...a power resistor, 12V Zener diode, 2 biasing resistors and a pot should get you in a good ballpark range for the throttle."

He knows more than me about this stuff....


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## major (Apr 4, 2008)

tenthousandclowns said:


> One wire, at the #2 position. The voltage is against the B-, so not isolated from the high voltage circuit.
> 
> I was thinking of adding the appropriate potentiometer so an isolated 12v dc-dc supply from the accessory 12v.
> 
> ...


That's a new one on me. Did you ask the seller for a connection diagram? Or at least a pinout for that Molex header. Chances are you'd need a signal there also.


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## tenthousandclowns (Jun 21, 2012)

Yeah, the top one is the KSI, and 2nd from the bottom is 'forward', which can likely be wired together for forward-only operation.

There is a manual that covers this version better than the usual one us on-road people have... it is more similar to some of the smaller controllers:

curtisinstruments.com/index.cfm?fuseaction=Products.DownloadPDF...1204X...


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## Graveaxis (Apr 1, 2015)

I also recently purchased the same controller and was able to get it wiring diagram from the original manufacturer. I am also unable to find a throttle that is applicable to this controller.


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## tenthousandclowns (Jun 21, 2012)

graveaxis, have you had any luck?


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## potvinguy (Jul 24, 2016)

Hey guys, I just wandered onto this post. I have a VW EV. I'm an EE and if you can give me a day or two I think I can design what you need.


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## tenthousandclowns (Jun 21, 2012)

thanks potvinguy.
the throttle is referenced against the HV pack... so we will run a wire from pack positive to the throttle and then step it down to 10.6v. One issue there is that pack voltage, for me at least, will vary from 130v to about 95v.

then there needs to be a pot that reduces the 10.6v down to 6.3v in a quarter turn of the pot... i could probably swing it a third of a turn if needed.

The curtis manual says this about 0-5v throttle inputs:
"A 0–5V throttle input option is also available for the 1204X/1205X/1209/1221
controllers. The negative side of the 5V source should be referenced to B- and
must be capable of driving an input impedance of 5kΩ"

so I assume the 5kohm impedance would be similar for the 6.3-10.6v throttle, but I have no way to know for sure.


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## potvinguy (Jul 24, 2016)

How do we know the control voltage is referenced to the traction battery?

And do you have a throttle pot now and what is it's value?


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## tenthousandclowns (Jun 21, 2012)

I realized that I don't know for sure.... I was basing that on the information for the 0-5v throttle in the curtis manual, and the fact that there is only one throttle pin and so the voltage has to come from somewhere. I just sent a message to the guy at FSIP who initially told me about this controller.

I think I have a 20kohm pot or something similar that I ordered a while back... thinking that a 1/4 turn would give 5kohms of variation.


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## potvinguy (Jul 24, 2016)

OK, you need to verify that we are using B- as the reference. Now here is a basic circuit:









The zener diode Z1 drops the voltage to a fixed 10.6. Then the pot varies the input to the Curtis. But you will need about 40% of a rotation to get to 6.3. The value of the pot doesn't matter; most of the EVs I've seen use a 5K pot, but if you have a 20k that's OK. We'll need to pick a zener and add a resistor or two to get the numbers exact.

I'm really curious where that odd input spec came from. It seems so arbitrary.

Let me know when you have confirmation, and I can pick the zener and finish the circuit design.


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## tenthousandclowns (Jun 21, 2012)

Yes, the guy at FSIP confirmed that the throttle voltage is against pack negative.

I would switch all this on and off with the ignition keyswitch I assume? Would that cause any issues with currents rushing in and out?

It is no problem to order a different pot... the usual curtis potboxes actually use 1/8 turn, not 1/4 turn as I was thinking.


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## potvinguy (Jul 24, 2016)

Just to confirm, FSIP said they would not change it back to normal for you? They don't sound very customer friendly.

Ask them if they know that the input impedance of this oddball is 5K. That is important to the final design, which I've been working on.


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## tenthousandclowns (Jun 21, 2012)

I asked them, haven't heard back yet.


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## tenthousandclowns (Jun 21, 2012)

I got the thing to work with one pot fixed at about 11kohm and a second pot swung by pedal action that adds about 10kohm of resistance over the course of its swing... I forget if it adds some kohms at the off position... 

forward and ksi pins got 12v, referenced against pack negative..

both the throttle and ksi are powered by the 12v system, run thru an isolator/regulator and then referenced to HV-

i don't have the car running yet so so far all i can say is the wheels spin up nicely...

I didn't put in any zener diodes.


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## tenthousandclowns (Jun 21, 2012)

Ok i have driven the van some but I never got much power out of this setup... i tried to tweak my adjuster pot for more power and then I got too much all of a sudden and it was never reliable after... so now I have the 10kohm pot being swung 1/8 turn and a little digital voltmeter as a load across the throttle signal... It still isn't very good, maybe something that draws a little bit less power than the digital voltmeter would make the voltage swing more nicely..


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## piotrsko (Dec 9, 2007)

Sounds like you burnt the carbon off the pot in a couple of places. Try another as a test.


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## tenthousandclowns (Jun 21, 2012)

AAugh.... i realized that i was burning up the clutch... because the power was coming too suddenly... this isn't such a complex thing i hope i can figure it out.


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