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
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-----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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