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  #71  
Old 06-28-2012, 12:56 PM
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Default Re: [EVDL] jumpy Pots

> I don't see why it is so hard to have a pot go from 0 to 100 ohms on the =
first
> half of the throw and 100 to 5000 ohms on the second half. It's the wa=
y a gas

> engine works.

I used to write firmware for electric fork lift controllers and we did this=
in firmware, i.e. interpret 0 to 2500 ohms as if it were 0 to 2% throttle =
and 2500 to 5k ohms as if 2% to 100% throttle. It was all to make the tr=
uck feel more like gas powered. Unless the microcontroller used was comp=
letely out of memory the feature was free and only involved a little time t=
o develop. I would sort of expect Curtis to have asimilarfeature, =
maybe on fancier controllers?

-Chris Darilek



________________________________
From: Lawrence Rhodes <xxx@xxx.xxx>
To: xxx@xxx.xxx.edu =

Sent: Thursday, June 28, 2012 1:16 PM
Subject: Re: [EVDL] jumpy Pots

[top]

I don't see why it is so hard to have a pot go from 0 to 100 ohms on the fi


rst =

half of the throw and 100 to 5000 ohms on the second half. It's the way =
a gas =

engine works. Electric has no lag therefore it's jerky. I have a stan=
dard =

Curtis pot and it is tricky to start. My daughter won't even drive it.=
I'd =

love to find a specialized pot. Maybe a series of pots in parallel or se=
ries. =

I start my ev in first gear and leave it there until I get to 25mph. Onc=
e =

started and rolling no problem. It's overcoming the start with just the rig=
ht =

push that is tricky. Worst case my car bucks like a bucking bronco. L=
awrence =

Rhodes....but it is possible but takes about 5 seconds to do smoothly.

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  #72  
Old 06-28-2012, 02:35 PM
EVDL List EVDL List is offline
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Default Re: [EVDL] jumpy Pots

Lawrence,
Is your pot the same setup as Lee explained for standard
Curtis - 5k is idle (no power) and 0 is max power?
there are not many pots that are reverse logarithmic,
where the are of small changes is at the high end of
the scale, while the large changes appear at the low
end of the scale.
It can be made of course, but that is not standard.
Also it is difficult to get right, if the small steps
all go from 5k to 4.7k and then it starts increasing
faster, while your controller only starts delivering
power when it sees the throttle go below 4.5k then
you are still missing all that fine control and
immediately jumping to the large steps.
So, sometimes it is better to have a linear pot
and convert the output to what you want to get,
either with series/parallel resistors or an
electronic conversion or - preferably - in software.

Regards,

Cor van de Water
Chief Scientist
Proxim Wireless Corporation http://www.proxim.com
Email: xxx@xxx.xxx Private: http://www.cvandewater.com
Skype: cor_van_de_water XoIP: +31877841130
Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203

-----Original Message-----
From: xxx@xxx.xxx.edu [mailto:xxx@xxx.xxx.edu] On
Behalf Of Lawrence Rhodes
Sent: Thursday, June 28, 2012 11:17 AM
To: xxx@xxx.xxx.edu
Subject: Re: [EVDL] jumpy Pots

I don't see why it is so hard to have a pot go from 0 to 100 ohms on the
first half of the throw and 100 to 5000 ohms on the second half. It's
the way a gas engine works. Electric has no lag therefore it's jerky.
I have a standard Curtis pot and it is tricky to start. My daughter
won't even drive it. I'd love to find a specialized pot. Maybe a
series of pots in parallel or series.
I start my ev in first gear and leave it there until I get to 25mph.
Once started and rolling no problem. It's overcoming the start with just
the right push that is tricky. Worst case my car bucks like a bucking
bronco. Lawrence Rhodes....but it is possible but takes about 5 seconds
to do smoothly.

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  #73  
Old 06-28-2012, 06:35 PM
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Default Re: [EVDL] jumpy Pots

[quote]On 28 Jun 2012 at 11:16, Lawrence Rhodes wrote:

> I don't see why it is so hard to have a pot go from 0 to 100 ohms on the first
> half of the throw and 100 to 5000 ohms on the second half. It's the way a gas
> engine works.

Two thoughts on this.

First, I understand why many builders (especially the major automakers) want
EVs to act like ICEVs - because that's what most drivers are used to.
Still, I find it annoying that they insist on building in a simulation of
automatic trans creep, which I consider one of the major downsides of a
slushbox. I also get my back up at the idea of adding noisemakers to an
inherently quiet EV, but that's a losing battle. Do I want them to simulate
ALL the action of an ICEV throttle in an EV? No thanks.

Second, not all ICEVs act that way. Indeed, I wish they would. My
workplace has a Mazda Tribute (Ford Explorer clone) and I find it impossible
to drive smoothly. All the throttle action happens in the first inch or so
of pedal travel. To make things worse, the pedal is stiffly spring so that
it acts almost like a toggle switch. When I try to pull away from a stop,
at first I get nothing, and then with a harder press, suddenly the machine
lunges ahead. My coworkers don't understand what I'm talking about when I
describe it, which leads me to suspect that this behavior isn't too uncommon
in ICEVs. It reminds me of the analog volume controls on cheap consumer
stereo outfits back in the 1980s, set so that the set was close to full
volume at about 12:00 position to make ignorant customers think it was more
powerful than the ones with smoother volume control.

David Roden - Akron, Ohio, USA
EVDL Administrator

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  #74  
Old 06-28-2012, 08:29 PM
EVDL List EVDL List is offline
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Default Re: [EVDL] jumpy Pots

I have a modified Curtis 1221B modified for 144vdc and needs 0 to 5K. So I'd
like very little change in the first half and most in the second half. Lawrence
Rhodes......

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