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EFIE with knobs
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cmac0351 Offline
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EFIE with knobs
I am trying to build an EFIE with knobs instead of the screwdriver adjustments. I have been unable to find 200k pots that are the right style, but I did find 250k. Does anyone know what changing that value will do? Should I try a lower or higher value? (Eagle Research schematic) On the ones I have built so far, I get an offset value of 20-470 millivolts. How will this change with a different pot installed?

I assume it is easier to fine tune the type of pot with a screwdriver, but I want to build on the other way.

Chris
12-10-2008 08:58 PM
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thomasbala Offline
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RE: EFIE with knobs
cmac0351 Wrote:I am trying to build an EFIE with knobs instead of the screwdriver adjustments. I have been unable to find 200k pots that are the right style, but I did find 250k. Does anyone know what changing that value will do? Should I try a lower or higher value? (Eagle Research schematic) On the ones I have built so far, I get an offset value of 20-470 millivolts. How will this change with a different pot installed?

I assume it is easier to fine tune the type of pot with a screwdriver, but I want to build on the other way.

Chris
Chris:
I think the easy answer is it won't make that much difference, however, I would do some testing using ohms law [ohm=volts/amps] and a digital volt meter before I finished assembly. Theoretically I think you should get a proportional + or - difference with the extra 50 ohms. Thus, since 50/250=20% the offset value would be between 16-564 volts.
12-10-2008 10:50 PM
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mike Offline
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RE: EFIE with knobs
250K will work fine for your pot. It will cause your top end voltage to be higher, but you can adjust your resistors if that's a problem.

How much did your 250K pot cost? Is it mult-turn? If so, what's the spec?

Thanks.

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12-11-2008 09:11 AM
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cmac0351 Offline
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RE: EFIE with knobs
I was looking at this one from mouser.com:

http://www.mouser.com/Search/ProductDeta...A3BQ%3d%3d

There is a link on that page to a .pdf of the catalog page to see a picture.

It is a linear taper pot like the ones people use with MAP enhancers. Is that good enough or would you know of something better?

mike Wrote:250K will work fine for your pot. It will cause your top end voltage to be higher, but you can adjust your resistors if that's a problem.

How much did your 250K pot cost? Is it mult-turn? If so, what's the spec?

Thanks.
12-11-2008 12:36 PM
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AlexR Offline
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RE: EFIE with knobs
cmac0351 Wrote:I am trying to build an EFIE with knobs instead of the screwdriver adjustments. I have been unable to find 200k pots that are the right style, but I did find 250k. Does anyone know what changing that value will do? Should I try a lower or higher value? (Eagle Research schematic) On the ones I have built so far, I get an offset value of 20-470 millivolts. How will this change with a different pot installed?

I assume it is easier to fine tune the type of pot with a screwdriver, but I want to build on the other way.

Chris

One thing to keep in mind here is your passengers in the car. People love touching things. First thing they'll do is point to the box you have and spin the knob...... there goes your setting..... if you want the knob feature then hide your EFIE where this can't happen.

Or install the James Bond ejection seat option under the passenger seat, but that's a whole different forum......

Alex

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12-11-2008 12:37 PM
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mike Offline
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RE: EFIE with knobs
cmac0351 Wrote:I was looking at this one from mouser.com:

http://www.mouser.com/Search/ProductDeta...A3BQ%3d%3d

There is a link on that page to a .pdf of the catalog page to see a picture.

It is a linear taper pot like the ones people use with MAP enhancers. Is that good enough or would you know of something better?

Ok, that's a single turn pot. It'll work OK. It's kind of hard to get the exact setting you want with a single turn pot, but it'll probably work fine. I wouldn't worry about the additional 50K. It'll just make your top end voltage higher than if it was 200K. But again, you can compensate for this by trying different resistors at R3 (I think it's R3 - but its' the one that is in line with the feed to the transformer) to adjust the top end back to where you want it.

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12-11-2008 12:48 PM
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cmac0351 Offline
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RE: EFIE with knobs
Yeah, they did that on Myth Busters. I will have to start that project after I get HHO going like I want it.


AlexR Wrote:Or install the James Bond ejection seat option under the passenger seat, but that's a whole different forum......
(This post was last modified: 12-11-2008 01:09 PM by cmac0351.)
12-11-2008 01:09 PM
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