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Re: [EVDL] Jumpy Pots

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#1 ·
Re: [EVDL] Jumpy Pots

I've had the same Curtis pot box in my EV for at least 3 years,
possibly up to 14 years old (I bought the car previously converted and
used). Currently my pot box is inside a weatherproof enclosure:

http://picasaweb.google.com/lh/photo/sby8m0mJDgKUTfUMTvYoVA?feat=3Ddirectli=
nk

it still works smoothly for me on a Kodiak controller

-Jon Glauser
http://jonglauser.blogspot.com
http://www.evalbum.com/555



soundboats <xxx@xxx.xxx.gov> wrote:
>
> Hello, I am trying to find out if anyone has had any luck in finding
> potentiometers that do not degrade with heavy use. I have tried the Cu=
rtis
> PB-6, a Chinese copy of the PB-6, and the Logisystem potboxes. All have
> suffered from the same degradation over time and last no more than 6-8
> months in heavy city and suburban driving (about 100 miles a week in stop
> and go traffic). The Logisystems potbox lasted only 2 months, the Curt=
is
> about 8 months, and the Chinese copy has been in for 6 months and showing
> signs of degradation.
> Initially all the potentiometers have a steady increase in resistance with
> the movement of the arm. However, the pots become progressively =93jum=
py,=94
> making driving difficult. I have measured the resistance and find that=
any
> small movement of the arm makes the resistance go up much higher for seco=
nd
> and then come down to what it should be. For example, if I have the ar=
m in
> a position that provides 1000 Ohms of resistance and move it just a few
> degrees the resistance jumps to 2500 Ohms before coming back down to 1200
> Ohms. This type of jump occurs at any setting of the arm and is not re=
lated
> to the controller. I have measured this jump when the pot boxes are
> disconnected from the controller as well.
> So, I am trying to find out if there is a brand of potentiometers that do
> not have this problem. I have found out that the resistance in these p=
ots
> is provided by a piecce of plastic, and I wonder if the plastic degrades
> with use. Any help would be welcome.
> Thanks,
> Tom Hruby
>
> --
> View this message in context: http://www.nabble.com/Jumpy-Pots-tp25648568=
p25648568.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Na=
bble.com.
>
>
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#27 ·
Re: [EVDL] jumpy Pots

Thank You, Lee!

A great no BS answer! JUST ordered TWO ,to reserect the pot boxes I have
kicking around with bum pots! 25k service factor SHOULD lastawile in my
Electrac AND car!Well, the Sentra I sold, with a Curtis, I'll KNOW he'll be
needing a pot, too? I like 8 bux, better than 50-70 anyhow!

Seeya

Bob
----- Original Message -----
From: "Lee Hart" <xxx@xxx.xxx>
To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
Sent: Tuesday, September 29, 2009 12:03 PM
Subject: Re: [EVDL] jumpy Pots


> Electric Blue auto convertions wrote:
>> I have only had 3 pots go bad so far and they were with in the first
>> year. NOW if you see what Fork lifts use, the same thing only built
>> much better and are still 5K ohm they last forever, BUT if you call
>> Hyster, Cat, or Clark they want between 50 and 70 $ for the pot
>> itself, is it worth it> thats up to you ..Wayne ev-blue.com
>
> Try MIL style RV4. There are many manufacturers (like the Allen Bradley
> type AB I mentioned, though Allen Bradley seems to have sold their pot
> business to someone, so it's under a new name). Here's an example from
> Digikey:
>
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=RV4N253C-ND
> http://www.precisionelectronics.com/MIL%20Style%20RV4%20PDF%20Download_files/MIL%20Style%20RV4.pdf
>
> Sealed, gold plated terminals, stainless steel shaft, 25,000 cycle
> rotational life, about $8.
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
> _______________________________________________
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> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>

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#28 ·
Re: [EVDL] Jumpy Pots

When you say 75deg, is that 75 real, as in less than 1/4 turn, or is it 75deg which is really 150deg or a bit less than 1/2 turn?

I have been able to find a few 90deg HE pots, and a few more 150deg...

I was also able to find a 90deg SEALED, IP rated, molded connector thingy that looked interesting... but I get concerned when they start saying electrical vs mechanical movement, etc...

Bob Sisson
1993 Geo Metro Convertible Project
Gaithersburg MD



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#29 ·
Re: [EVDL] jumpy Pots

T24gVHVlLCBTZXAgMjksIDIwMDkgYXQgNTozMSBQTSwgQm9iIFJpY2UgPGJvYnJpY2VAc25ldC5u
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aXN0aW5mby9ldgoK
 
#30 ·
Re: [EVDL] jumpy Pots

Bob Rice wrote:
> Thank You, Lee!
>
> A great no BS answer! JUST ordered TWO ,to reserect the pot boxes I have
> kicking around with bum pots! 25k service factor SHOULD lastawile in my

25K sounded kinda minimal to me. Isn't that one for each throttle
movement? Might that be around ten per mile? 2500 miles?

--
Willie, ONWARD! Through the fog!
http://counter.li.org Linux registered user #228836 since 1995
Debian3.1/GNU/Linux system uptime 654 days 5 hours 52 minutes

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#31 ·
Re: [EVDL] Jumpy Pots

I have never put it in a sealed box, just mounted it up high in the engine
bay - and never had problems with them. And this is mostly in the wet
Pacific NW. They are fairly well sealed, I think, for casual road
spray/dirt.

Joseph H. Strubhar

Web: www.gremcoinc.com

E-mail: xxx@xxx.xxx


----- Original Message -----
From: "Ben" <xxx@xxx.xxx>
To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
Sent: Tuesday, September 29, 2009 7:31 AM
Subject: Re: [EVDL] Jumpy Pots


>
soundboats <xxx@xxx.xxx.gov> wrote:
>>
>> I will explore some of the options suggested:
>> 1. check out pots from fork lifts
>> 2. check out throttle position sensors from autos
>> 3. find out if the Logisystem controller I have can be run with a Hall
>> effect sensor
>> 4. Check out cleaning the pots with Cramolin red. I still have my two old
>> pots that have gone bad, so cleaning one and checking it is no extra cost
>> for me.
>>
>>
>
> How about 5. Check the mounting situation for exposure to the elements
>
> This topic comes up often, and it's always a chorus of people on both
> sides of the issue - either their pots work fine for years, or they go
> bad as quickly as yours do. Is it in a sealed box, away from any
> exposure to moisture, motor dust, road dirt? Or maybe there's some
> trick to orientation that makes crude accumulate on the resistive
> element for some people and not so much for others.
>
> Just a few more ideas. Good luck.
>
> Ben
>
> _______________________________________________
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>


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#32 ·
Re: [EVDL] jumpy Pots

----- Original Message -----
From: "Willie McKemie" <xxx@xxx.xxx>
To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
Sent: Tuesday, September 29, 2009 12:53 PM
Subject: Re: [EVDL] jumpy Pots


>
Bob Rice wrote:
>> Thank You, Lee!
>>
>> A great no BS answer! JUST ordered TWO ,to reserect the pot boxes I
>> have
>> kicking around with bum pots! 25k service factor SHOULD lastawile in my
>
> 25K sounded kinda minimal to me. Isn't that one for each throttle
> movement? Might that be around ten per mile? 2500 miles?

Good point, but I would HOPE that the 25001'st movement won't be it's
last<g>?!
> --
> Willie, ONWARD! Through the fog!
> http://counter.li.org Linux registered user #228836 since 1995
> Debian3.1/GNU/Linux system uptime 654 days 5 hours 52 minutes
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>

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#33 ·
Re: [EVDL] Jumpy Pots

How about a vane with a variable width slot cut in it, an LED, and an LDR?
Jut put it in a lightproof, dustproof box. Tweak the slot to get the taper
you like.

David Roden - Akron, Ohio, USA
EVDL Administrator

= = = = = = = = = = = = = = = = = = = = = = = = = = = = =
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#34 ·
Re: [EVDL] jumpy Pots

Evan Tuer wrote:
>
Bob Rice <xxx@xxx.xxx> wrote:
>> Thank You, Lee!
>>
>> A great no BS answer! JUST ordered TWO ,to reserect the pot boxes I have
>> kicking around with bum pots! 25k service factor SHOULD lastawile in my
>> Electrac AND car!Well, the Sentra I sold, with a Curtis, I'll KNOW he'll be
>> needing a pot, too? I like 8 bux, better than 50-70 anyhow!
>
> Weel, you get what you pay for... A real throttle pot might cost 10
> times as much but will last 200 times as long. How much is your time
> worth, swapping it out every few years?

The original Curtis (Cursit, as Bob might say) pot in my EV failed in
the first year. I replaced it with one of these, and it's still working
10 years later. I suspect the 25k rotational life is pretty conservative
-- for instance, it might mean 25k turns until the resistance changes by 1%.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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#35 ·
Re: [EVDL] jumpy Pots

From: "Willie McKemie"
> 25K sounded kinda minimal to me. Isn't that one for each throttle
> movement? Might that be around ten per mile? 2500 miles?

I don't know. I suspect that spec is pretty conservative. I've had one
in my EV for 10 years now without it failing. The original Curtis pot
lasted 1 year.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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#36 ·
Re: [EVDL] Jumpy Pots

> ----- Original Message -----
> From: "David Roden" <xxx@xxx.xxx>
> To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
> Subject: Re: [EVDL] Jumpy Pots
> Date: Tue, 29 Sep 2009 14:29:37 -0400
>
>
> How about a vane with a variable width slot cut in it, an LED, and an LDR?
> Jut put it in a lightproof, dustproof box. Tweak the slot to get the taper
> you like.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
David, I liked your approach, but I cannot locate a LDR
that goes down near zero ohms.

The real cure will take an
adapter board specifically designed for each controller
"Pot input" to interface with a long lived sensor
technology Manufactured in long lived materials for a
retail price under $8.95. (;o> (That is Lee's cost for a
replacement high quality pot.)

So, lets ask the controller manufacturers to "Dump the pot!
and use another control sensor system.

I have always felt the "throttle" sensor should be
inside the cabin, above the petal.

And the controller inside the firewall behind the
glove box in a box/duct with forced air cooling dumped
outside by duct except when needed to warm/dry the
inside of the windshield, when it is directed to the
defroster ducts. (Why "Waste" the heat?)

With High Regards,

Dennis Miles, (Director)
Electric Vehicle Training Institute
in Central Florida


--
An Excellent Credit Score is 750
See Yours in Just 2 Easy Steps!


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#37 ·
Re: [EVDL] Jumpy Pots

Let the LDR be the bottom resistor of a divider on the gate of a FET.

Regards,

Cor van de Water
Director HW & Systems Architecture Group Proxim Wireless
Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: xxx@xxx.xxx
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
Behalf Of Dennis Miles
Sent: Wednesday, September 30, 2009 5:14 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Jumpy Pots


> ----- Original Message -----
> From: "David Roden" <xxx@xxx.xxx>
> To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
> Subject: Re: [EVDL] Jumpy Pots
> Date: Tue, 29 Sep 2009 14:29:37 -0400
>
>
> How about a vane with a variable width slot cut in it, an LED, and an
LDR?
> Jut put it in a lightproof, dustproof box. Tweak the slot to get the
> taper you like.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
David, I liked your approach, but I cannot locate a LDR that goes
down near zero ohms.

The real cure will take an
adapter board specifically designed for each controller "Pot input" to
interface with a long lived sensor technology Manufactured in long lived
materials for a retail price under $8.95. (;o> (That is Lee's cost for
a replacement high quality pot.)

So, lets ask the controller manufacturers to "Dump the pot!
and use another control sensor system.

I have always felt the "throttle" sensor should be inside the cabin,
above the petal.

And the controller inside the firewall behind the glove box in a
box/duct with forced air cooling dumped outside by duct except when
needed to warm/dry the inside of the windshield, when it is directed to
the defroster ducts. (Why "Waste" the heat?)

With High Regards,

Dennis Miles, (Director)
Electric Vehicle Training Institute
in Central Florida


--
An Excellent Credit Score is 750
See Yours in Just 2 Easy Steps!


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#39 ·
Re: [EVDL] Jumpy Pots

Cor van de Water wrote:
> Let the LDR be the bottom resistor of a divider on the gate of a FET.

I think you'd have trouble with variations between parts, and due to
temperature. The gate threshold voltage of a FET has a very wide spread.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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#38 ·
Re: [EVDL] Jumpy Pots

>> How about a vane with a variable width slot cut in it, an LED, and an LDR?
>> Jut put it in a lightproof, dustproof box. Tweak the slot to get the taper
>> you like.
>>
>> David Roden - Akron, Ohio, USA
>> EVDL Administrator
>>
>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Dennis Miles wrote:
> David, I liked your approach, but I cannot locate a LDR
> that goes down near zero ohms.

It doesn't have to go to zero ohms. The operational range (for a Curtis
controller -- most others are similar) is 300-4300 ohms. Anything under
300 ohms is interpreted as "shorted wires", and the controller turns
off. Likewise, anything over 4300 ohms is interpreted as "broken wires"
and the controller turns off.

It's easy to get a photoresistive cell to cover this range. But, I
wouldn't try to use a narrow slot to "throttle" the light. Instead, I'd
use a two disks of polarized plastic. One is fixed, and the other
rotates 90 degrees as the potbox lever is moved. When the polarized
disks are aligned, they are clear and essentially all the light goes
through. When one is rotated 90 degrees, they are cross-polarized and
essentially no light gets through.

Then, I would add a pair of fixed resistors; one in series with the
photoresistor to set the minimum 'off' resistance to about 300 ohms; and
a resistor in parallel so the 'full throttle' resistance doesn't go over
4300 ohms.

> So, lets ask the controller manufacturers to "Dump the pot!
> and use another control sensor system.

There's nothing intrinsically wrong with a pot. The problems are caused
by a *cheap* pot.

You will have the same problems with a cheap hall-effect sensor, or
cheap inductive sensor.

The key is to use good quality parts, no matter what technology it
happens to be!

> And the controller inside the firewall behind the
> glove box in a box/duct with forced air cooling dumped
> outside by duct except when needed to warm/dry the
> inside of the windshield, when it is directed to the
> defroster ducts. (Why "Waste" the heat?)

The controller is never hot enough (or *shouldn't be hot enough) to
serve as a heater or defroster. About the best you could do is use it as
a preheater for cabin air, followed by your regular heater.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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#41 ·
Re: [EVDL] Jumpy Pots

In cases where the TPS is actually used to directly control the throttle
(throttle by wire) as is done on some new european cars, they use paired
hall effect sensors 90 degrees out of phase, If the 2 sensors don't
agree to within some small error margin the controller will lock out and
the car won't start.

In a "safety critical" situation like an accelerator pedal, having a
single point of failure like a 25 cent pot that is known to also be
unreliable and fail in unpredictable ways is not acceptable.

Its only got to jump once in a car park and squish some kid and your
going to have a bad day, I know you have kill switches and the like but
its all a bit late.

With some electronics you could get the 0-5k equivalent readout that the
Curtis wants from a twin hall sensor mounted to the accelerators point
of rotation, or worst case a separate cable box inside the cab.
serial that data to another highly robust micro at the Curtis to feed it
the 0-5k, that way the long communications run is digital and won't pick
up noise from motors etc, If the comms line starts to fail the
accelerator box starts buzzing, If there is a complete failure the
remote station commands 0 output to the Curtis and also starts bitching
at you.

I was looking at making a similar system, "throttle by wire" for gokarts
to comply with some law changes here (Australia) what level of interest
is there in this as a product for cars?

Probably looking in the $150-200 range for the complete assembly with
the dual hall sensors, programmable (multi point) throttle curve,
calibration etc.


Cor van de Water wrote:
> Let the LDR be the bottom resistor of a divider on the gate of a FET.
>
> Regards,
>
> Cor van de Water
> Director HW & Systems Architecture Group Proxim Wireless
> Corporation http://www.proxim.com
> Email: xxx@xxx.xxx Private: http://www.cvandewater.com
> Skype: cor_van_de_water IM: xxx@xxx.xxx
> Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
> Tel: +91 (040)23117400 x203 XoIP: +31877841130
>
> -----Original Message-----
> From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
> Behalf Of Dennis Miles
> Sent: Wednesday, September 30, 2009 5:14 AM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Jumpy Pots
>
>
>
>> ----- Original Message -----
>> From: "David Roden" <xxx@xxx.xxx>
>> To: "Electric Vehicle Discussion List" <xxx@xxx.xxx.edu>
>> Subject: Re: [EVDL] Jumpy Pots
>> Date: Tue, 29 Sep 2009 14:29:37 -0400
>>
>>
>> How about a vane with a variable width slot cut in it, an LED, and an
>>
> LDR?
>
>> Jut put it in a lightproof, dustproof box. Tweak the slot to get the
>> taper you like.
>>
>> David Roden - Akron, Ohio, USA
>> EVDL Administrator
>>
>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>>
> David, I liked your approach, but I cannot locate a LDR that goes
> down near zero ohms.
>
> The real cure will take an
> adapter board specifically designed for each controller "Pot input" to
> interface with a long lived sensor technology Manufactured in long lived
> materials for a retail price under $8.95. (;o> (That is Lee's cost for
> a replacement high quality pot.)
>
> So, lets ask the controller manufacturers to "Dump the pot!
> and use another control sensor system.
>
> I have always felt the "throttle" sensor should be inside the cabin,
> above the petal.
>
> And the controller inside the firewall behind the glove box in a
> box/duct with forced air cooling dumped outside by duct except when
> needed to warm/dry the inside of the windshield, when it is directed to
> the defroster ducts. (Why "Waste" the heat?)
>
> With High Regards,
>
> Dennis Miles, (Director)
> Electric Vehicle Training Institute
> in Central Florida
>
>
> --
> An Excellent Credit Score is 750
> See Yours in Just 2 Easy Steps!
>
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/ Usage guidelines:
> http://evdl.org/help/index.html#conv
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>
>
> _______________________________________________
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>
>

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#40 ·
Re: [EVDL] Jumpy Pots

> ----- Original Message -----
> From: "Lee Hart" <xxx@xxx.xxx>
>
> The key is to use good quality parts, no matter what technology it
> happens to be!
>
> > And the controller inside the firewall behind the glove box in a
> > box/duct with forced air cooling dumped outside by duct except
> > when needed to warm/dry the inside of the windshield, when it is
> > directed to the defroster ducts. (Why "Waste" the heat?)
>
> The controller is never hot enough (or *shouldn't be hot enough) to
> serve as a heater or defroster. About the best you could do is use it as
> a preheater for cabin air, followed by your regular heater.
>
That is dependent upon climate, here in the Tampa Bay Area, only a small
amount of heat is needed, in fact some EV builders just use cabin air as a
de-fogger, with no heat at all! Happily, we do not all live in Minnesota.
(;> Dennis
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
>


--
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#42 ·
Re: [EVDL] jumpy Pots

This thread has me curious... I just bought a replacement potentiometer
for my truck. I haven't had any problems but I wanted to find a good
replacement part for a friend, so I tried a Honeywell/Clarostat from
Mouser. So far so good, but what surprised me was the potentiometer I
replaced was also a Clarostat. Did Curtis use this brand or did someone
replace it before I bought the truck ten years ago? I never had any
problems with it, so it seems like a good quality component.

Nick



Lee Hart wrote:
> Electric Blue auto convertions wrote:
>> I have only had 3 pots go bad so far and they were with in the first
>> year. NOW if you see what Fork lifts use, the same thing only built
>> much better and are still 5K ohm they last forever, BUT if you call
>> Hyster, Cat, or Clark they want between 50 and 70 $ for the pot
>> itself, is it worth it> thats up to you ..Wayne ev-blue.com
>
> Try MIL style RV4. There are many manufacturers (like the Allen Bradley
> type AB I mentioned, though Allen Bradley seems to have sold their pot
> business to someone, so it's under a new name). Here's an example from
> Digikey:
>
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=RV4N253C-ND
> http://www.precisionelectronics.com/MIL%20Style%20RV4%20PDF%20Download_files/MIL%20Style%20RV4.pdf
>
> Sealed, gold plated terminals, stainless steel shaft, 25,000 cycle
> rotational life, about $8.

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#43 ·
Re: [EVDL] jumpy Pots

Nick wrote:
> This thread has me curious... I just bought a replacement potentiometer
> for my truck. I haven't had any problems but I wanted to find a good
> replacement part for a friend, so I tried a Honeywell/Clarostat from
> Mouser. So far so good, but what surprised me was the potentiometer I
> replaced was also a Clarostat. Did Curtis use this brand or did someone
> replace it before I bought the truck ten years ago? I never had any
> problems with it, so it seems like a good quality component.

The one I replaced in my old Curtis potbox was a Clarostat, too. It is a
special order, with its resistance element crowded to one end. But the
series it is in is a cheap unsealed consumer grade pot.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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#44 ·
Re: [EVDL] Jumpy Pots

soundboats wrote -

> Small cars may have a
> problem in using the Logisystems pot box because the travel in the
> throttle
> cable is too short to accommodate an 110 degree range.

Change the length of the throw by changing the geometry, add a pulley and
experiment with the pot/pulley/pedal distance to get the correct length.

Rush
Tucson AZ

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#45 ·
Re: [EVDL] jumpy Pots

The MIL spec pots sound interesting, but I should put out a word of caution.
The Logisystems pot was supposed to have been one of the MIL spec ones but
it failed in 2 months. The other point is to make sure you buy a pot with a
linear response. The Logisystem pot had the logarithmic response and that
proved very difficult for driving in the city. I had to depress my pedal
almost half-way to get started and then the acceleration was too fast.
Tom Hruby



Lee Hart wrote:
>
> Evan Tuer wrote:
>>
Bob Rice <xxx@xxx.xxx> wrote:
>>> Thank You, Lee!
>>>
>>> A great no BS answer! JUST ordered TWO ,to reserect the pot boxes I
>>> have
>>> kicking around with bum pots! 25k service factor SHOULD lastawile in my
>>> Electrac AND car!Well, the Sentra I sold, with a Curtis, I'll KNOW he'll
>>> be
>>> needing a pot, too? I like 8 bux, better than 50-70 anyhow!
>>
>> Weel, you get what you pay for... A real throttle pot might cost 10
>> times as much but will last 200 times as long. How much is your time
>> worth, swapping it out every few years?
>
> The original Curtis (Cursit, as Bob might say) pot in my EV failed in
> the first year. I replaced it with one of these, and it's still working
> 10 years later. I suspect the 25k rotational life is pretty conservative
> -- for instance, it might mean 25k turns until the resistance changes by
> 1%.
>
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>

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#46 ·
Re: [EVDL] jumpy Pots

soundboats wrote:
> The MIL spec pots sound interesting, but I should put out a word of
> caution. The Logisystems pot was supposed to have been one of the MIL
> spec ones but it failed in 2 months. The other point is to make sure
> you buy a pot with a linear response. The Logisystem pot had the
> logarithmic response and that proved very difficult for driving in
> the city. I had to depress my pedal almost half-way to get started
> and then the acceleration was too fast.

Sounds like they sent the wrong pot. The one I provided the Digikey
part# for is a linear taper.

Another caveat: Look at your potbox, and see what angle it actually
rotates the arm over. My old one (that I fixed with the 25K pot) moves
over just under a 90 degree arc. But in the current Curtis data sheet,
it says 45 degrees of rotation. This would require a 50K pot to get an
adequate resistance change.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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#47 ·
Re: [EVDL] jumpy Pots

Lee,
The Curtis box I have has a 75 degree rotation. It must be one of the older
ones. The Chinese copy of the Curtis has an 80 degree rotation.
Tom



Lee Hart wrote:
>
> soundboats wrote:
>> The MIL spec pots sound interesting, but I should put out a word of
>> caution. The Logisystems pot was supposed to have been one of the MIL
>> spec ones but it failed in 2 months. The other point is to make sure
>> you buy a pot with a linear response. The Logisystem pot had the
>> logarithmic response and that proved very difficult for driving in
>> the city. I had to depress my pedal almost half-way to get started
>> and then the acceleration was too fast.
>
> Sounds like they sent the wrong pot. The one I provided the Digikey
> part# for is a linear taper.
>
> Another caveat: Look at your potbox, and see what angle it actually
> rotates the arm over. My old one (that I fixed with the 25K pot) moves
> over just under a 90 degree arc. But in the current Curtis data sheet,
> it says 45 degrees of rotation. This would require a 50K pot to get an
> adequate resistance change.
>
> --
> Lee A. Hart | Ring the bells that still can ring
> 814 8th Ave N | Forget the perfect offering
> Sartell MN 56377 | There is a crack in everything
> leeahart earthlink.net | That's how the light gets in -- Leonard Cohen
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
>
>

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#48 ·
Re: [EVDL] jumpy Pots

soundboats wrote:
> Lee,
> The Curtis box I have has a 75 degree rotation. It must be one of the older
> ones. The Chinese copy of the Curtis has an 80 degree rotation.

Yes, that's what mine has. But the newer Curtises have a 45 deg. rotation.

--
Lee A. Hart | Ring the bells that still can ring
814 8th Ave N | Forget the perfect offering
Sartell MN 56377 | There is a crack in everything
leeahart earthlink.net | That's how the light gets in -- Leonard Cohen

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#49 ·
Re: [EVDL] jumpy Pots

On 30 Sep 2009 at 10:59, Lee Hart wrote:

> But the newer Curtises have a 45 deg. rotation.
>

FWIW, I had a very old potbox for my PMC DCC-96 (before they became Curtis)
that had a cable, spring, and pulley lashup inside. It converted the arm's
rotation (90 degrees, IIRC) into 270 degree pot rotation. That's the only
one I've ever seen that was made that way.

David Roden - Akron, Ohio, USA
EVDL Administrator

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#50 ·
Re: [EVDL] Jumpy Pots

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#51 ·
Re: [EVDL] Jumpy Pots

You cannot put pack (120V) voltage on a 5k pot as it will
burn up from the power dissipated in it.
Though I would expect that they typically use 12V to get
the reading from the throttle pot - or if the pack is
below 48V they may still use that directly...

Regards,

Cor van de Water
Director HW & Systems Architecture Group Proxim Wireless
Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water IM: xxx@xxx.xxx
Tel: +1 408 383 7626 VoIP: +31 20 3987567 FWD# 25925
Tel: +91 (040)23117400 x203 XoIP: +31877841130

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
Behalf Of soundboats
Sent: Thursday, October 01, 2009 1:27 AM
To: xxx@xxx.xxx.edu
Subject: Re: [EVDL] Jumpy Pots


Hello everyone who responded.
I am starting a new thread on this subject since it is getting very
confusing to follow who said what.
So I thought I would summarize some of the information I have gleaned
from this discussion and put it all in one place, and of course leave
you with more questions.

1. The basic problem seems to be that the standard potentiometers are
getting contaminated with dust or other debris, and sealing the box
would probably prevent the degradation. I will try this first since I
have replaced the potentiometer in the PB-6 box I have with one I
purchased from EVParts.

2. It might be possible to find a MIL spec pot (either carbon or plastic
based)that is sealed and meets the the resistance and "travel"
requirements for my throttle. These are rated at 25,000 cycles which
however does not really meet my needs. I did a simple calculation on my
lunch break and found that I cycle the throttle/pot about 10 times per
mile in the city driving I do. This means the pot would be rated for
only 2500 miles or about 8 months of my driving.

3. It is possible to find a pot from a electric fork lift that is rated
much higher, but it costs about $75. I have not tried to do this yet.

4. Some of you have suggest Hall effect potentiometers. I looked into
them but found that they are rated only for 4-5 volts inputs. I believe
both the Curtis and Logisystem controllers put out the full battery pack
voltage to the pot (120 volts in my case). Only the Kelly's put out 5
volts to the pot.
If anyone out there knows more about this please let us all know!!! It
would be interesting to try a Hall effect pot.

Tom Hruby


soundboats wrote:
>
> Hello, I am trying to find out if anyone has had any luck in finding
> potentiometers that do not degrade with heavy use. I have tried the
> Curtis PB-6, a Chinese copy of the PB-6, and the Logisystem potboxes.

> All have suffered from the same degradation over time and last no more

> than
> 6-8 months in heavy city and suburban driving (about 100 miles a week
> in stop and go traffic). The Logisystems potbox lasted only 2 months,

> the Curtis about 8 months, and the Chinese copy has been in for 6
> months and showing signs of degradation.
> Initially all the potentiometers have a steady increase in resistance
> with the movement of the arm. However, the pots become progressively
"jumpy,"
> making driving difficult. I have measured the resistance and find
> that any small movement of the arm makes the resistance go up much
> higher for second and then come down to what it should be. For
> example, if I have the arm in a position that provides 1000 Ohms of
> resistance and move it just a few degrees the resistance jumps to 2500

> Ohms before coming back down to 1200 Ohms. This type of jump occurs
> at any setting of the arm and is not related to the controller. I
> have measured this jump when the pot boxes are disconnected from the
controller as well.
> So, I am trying to find out if there is a brand of potentiometers that

> do not have this problem. I have found out that the resistance in
> these pots is provided by a piecce of plastic, and I wonder if the
> plastic degrades with use. Any help would be welcome.
> Thanks,
> Tom Hruby
>
>

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