[EVDL List]

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


[quote]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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[EVDL List]

Smoking pot again, eh.


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


_______________________________________________
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Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
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[EVDL List]

Years ago I needed to retrofit a large analog system that had several potentiometers with a programmer to emulate different pot settings. I experimented with photoresistor/LED combinations in heat shrink housings piggybacked on the pots, but these were not very repeatable. Not only that, the photoresistors (from Radio Shack) tended to have light-history memory. What I ended up using were Vactecs:

http://users.rcn.com/oakridge.ma.ultranet/Products/Vactrol.html

These were very repeatable and predictable, and surprisingly fast. Of course for a pedal application, you would most likely drive the lamp with a voltage from a pot, which just brings us back to the original problem. However, I would think such a setup would nicely filter out scratchiness.

Best Regards,

- Gene



-----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


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Usage guidelines: http://evdl.org/help/index.html#conv
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[EVDL List]

[quote]On 30 Sep 2009 at 16:24, Gene Stopp wrote:

> What I ended up using were Vactecs:
>
> http://users.rcn.com/oakridge.ma.ultranet/Products/Vactrol.html
>
> These were very repeatable and predictable, and surprisingly fast. Of course
> for a pedal application, you would most likely drive the lamp with a voltage
> from a pot, which just brings us back to the original problem. However, I
> would think such a setup would nicely filter out scratchiness.

That's exactly the sort of solution I suggested the last time we had this
discussion on the EVDL.

Over 30 years ago, I used audio consoles in which the faders were based on
this idea. The dirt-cheap potentiometers on the console actually controlled
the brightness of incandescent lamps, which shone on CdS cells (LDRs). They
were made by Sparta, IIRC.

They turned oiut to be major headaches for the audio engineers. It was
almost impossible to keep the stereo channels in balance over the entire
range of the fader. This pretty clearly shows the inherent stability
problem.

However, I don't think that would matter very much for an EV controller.
The only problem I can see is if the lamp were to burn out. You'd need a
resistance-limiting safeguard to make sure the controller wouldn't go full
speed ahead in that instance. (The lamps in the Sparta consoles almost
never failed, btw; they were run well below their rated voltage.)

David Roden - Akron, Ohio, USA
EVDL Administrator

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[EVDL List]

[quote]soundboats wrote:
> 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.

A good idea, given that you already have the pot. But the fundamental
problem is caused by a cheap unsealed pot. Sealing up the potbox will
help, but it won't retrofit quality into a cheap pot.

> 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.

The one I mentioned is just one I used that's better than the original.
It's not the "ideal" solution, developed from an exhaustive analysis and
search. It's just the first one I found that was better than what I had.

You can buy pots with arbitrarily good specs. The ones used in mass
produced cars are certainly better than what I used -- but they are hard
to buy in single-piece quantities without the ridiculous mark-ups (a ten
cent bolt from the hardware store costs $10 at your auto dealer).

So, do your own research. The electronics distributors have literally
hundreds of pots to choose from. Look up their specifications until you
find one with good enough specs to satisfy you. The better the pot, the
higher the price, of course.

> 3. It is possible to find a pot from a electric fork lift that is
> rated much higher, but it costs about $75.

I'll bet you'll find that inside that $75 forklift potbox is a $5 or $10
pot from the Digikey or Mouser catalogs.

> 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.

Hall effect sensors are a good solution if you're designing the
controller to match. But they are hard to retrofit onto a controller
that was designed for a resistive potentiometer.

--
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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[EVDL List]

I have the impression that with the pedal pot driving a Vactec
you are using too many parts and still have the problem of the
"worn through spot" on the pedal pot where you spend most of
the time (unless you are one of the ON/OFF type drivers)
Anyhow, the incandescent lamp and CdS setup is exactly what
is needed - plus a moving vane in between, so that the light
from the lamp can be extinguished by the vane and the value
of the CdS cell controlled from min to max resistance.
Looking at the Vactrol VTLA37 resistance/time graph I see
that it reaches less than 200 and over 10kOhm within 100ms
after application of Full on/off lamp brightness, so I would
venture a guess that adding a vane in between might increase
the ON resistance slightly (more distance between lamp/cell)
but we only need to be <500 Ohm for a throttle pot.
To limit the max resistance simply add a fixed 4.7kOhm in
parallel to the CdS cell, however it may be preferable to
never allow the vane to completely block the light and keep
the CdS below 5kOhm with the remaining lamp light, so that
if the lamp dies (or the CdS cell) then the resistance is
above 5k and the controller will fault, instead of possibly
going full throttle. (depending if 5k is low or high throttle)

So, this brings us back to a suggestion already made before...
NOTE that the vane and the Vactec (or discrete lamp + CdS cell)
must be shielded from ambient light, otherwise you will only
be able to drive at night!
I think I have seen this type of control in some instruments
in the past, I think it was in some old electronic organs and
in sewing machine foot pedals in conjunction with a TRIAC.

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 Gene Stopp
Sent: Thursday, October 01, 2009 4:54 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Jumpy Pots

Years ago I needed to retrofit a large analog system that had several
potentiometers with a programmer to emulate different pot settings. I
experimented with photoresistor/LED combinations in heat shrink housings
piggybacked on the pots, but these were not very repeatable. Not only
that, the photoresistors (from Radio Shack) tended to have light-history
memory. What I ended up using were Vactecs:

http://users.rcn.com/oakridge.ma.ultranet/Products/Vactrol.html

These were very repeatable and predictable, and surprisingly fast. Of
course for a pedal application, you would most likely drive the lamp
with a voltage from a pot, which just brings us back to the original
problem. However, I would think such a setup would nicely filter out
scratchiness.

Best Regards,

- Gene



-----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


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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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[EVDL List]

This post by Tom exactly describes the symptoms my PB6 is displaying. It
started a few weeks ago and is getting worse. The car has about 8 months on
it, same as when Tom's started acting up. Anyone found a better solution
than the PB6? The controller is a Curtis 1238-7501.
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[EVDL List]

I've recently had a problem in my conversion which I thought might be jumpy
pots also. It turns out (I think) that it was a symptom of the 12V battery
dying. Since that battery keeps the contactor closed, things could
obviously get weird when it was starting to be at a threshold voltage.
After dropping further, the 12V battery got to the point it wouldn't keep
the contactor open and the car stopped.

The conversion had previously been using a separate 12V charger that I think
has died. It is now time to bump up the DC-DC converter installation in
priority.

My symptom was a surging and jerking under acceleration. Now, I think it
was because the contactor was briefly cutting out.

Mike

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On Behalf
Of tomw
Sent: Sunday, August 22, 2010 7:21 PM
To: xxx@xxx.xxx.edu
Subject: Re: [EVDL] Jumpy Pots


This post by Tom exactly describes the symptoms my PB6 is displaying. It
started a few weeks ago and is getting worse. The car has about 8 months on
it, same as when Tom's started acting up. Anyone found a better solution
than the PB6? The controller is a Curtis 1238-7501.
--
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2965p2334529.html
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[EVDL List]

Thanks Wistar, I will see if I can get a replacement. Thanks also to Bill
and Mike. I will keep those possibilities in mind. I found that EVWorks
offers a Hall Effect throttle that is a bolt in replacement for the PB6. It
appears this would work for my car as I can reprogram the controller to use
this "type 2" throttle. I also found a Honeywell/Clarion industrial pot
(#380C325K) at Digikey with 100,000 cycle rotational life. It is a 312
degree pot, and my PB6 looks to be about 45 degree. A 25k version would
then give about 3.6V max voltage, and the max voltage setpoint in the
controller software currently is 3.5V, so that seems about right. The Hall
Effect is a better long term solution, and it appears I can do it with
existing wiring in the harness, just switching connection on one wire to get
a ground, and adding in a 5V regulator at the throttle pot powered off the
12V to the microswitch. Some details to work out though, like current
requirements.
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[EVDL List]

Hello to another Tom,

Sorry to be so late in responding, but I just got back from vacation.

I found that the Chinese copy of the PB-6 that is available from several
vendors has worked out better than the PB-6. I also tried the
replacement pot that is sold by EV-parts, but that proved to be bad from
the beginning. The discussion around my first comments suggested that
the issue was dirt getting into the box. I taped my Chinese copy around
all the open edges and that seems to have improved the situation. My
Chinese copy has now been installed for over a year without any
problems. However, I do suspect that it may go soon. It is showing
some instability when the outside temperature goes above 90 degrees.



My Logisystems controller blew out for the second time and so I am now
switching and will try the NetGain controller that has the Hall effect
throttle. I hope that works out better.



Tom



From: tomw [via Electric Vehicle Discussion List]
[mailto:ml-node+xxx@xxx.xxxle.com]
Sent: Sunday, August 22, 2010 6:21 PM
To: Hruby, Tom (ECY)
Subject: Re: Jumpy Pots



This post by Tom exactly describes the symptoms my PB6 is displaying.
It started a few weeks ago and is getting worse. The car has about 8
months on it, same as when Tom's started acting up. Anyone found a
better solution than the PB6? The controller is a Curtis 1238-7501.

________________________________

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