How to feed an original tachometer?

Technical discussion on converting internal combustion to electric
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evric
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How to feed an original tachometer?

Post by evric » Thu, 16 Apr 2009, 19:56

Peter, I have updated the tacho circuit in the post up above. Yes I did test the circuit and it moves the pointer on the tacho.
This circuit is additional to that one and I use it to protect the motor from overspeed. If the motor exceeds approx. 6,000 RPM (eg. full throttle in neutral)this circuit will short out the potbox which will result in 0 RPM. This is self resetting after a few seconds.

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Peter C in Canberra
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How to feed an original tachometer?

Post by Peter C in Canberra » Thu, 16 Apr 2009, 21:23

Great. I'll try part 1, moving the tacho pointer, and this limiter circuit later. You could probably do a roaring trade in these made up nicely in a little box.
thanks,
Peter.
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How to feed an original tachometer?

Post by Peter C in Canberra » Sat, 18 Apr 2009, 04:35

It occurs to me that a useful addition to the over-reving circuit could be a buzzer. One way to over rev would be the one suggested, namely accelerator pedal while in neutral or driving in too low gear, and the circuit would work for that. Another way would be to use low gear to get up a steep hill and forgetting to change up at the top. One could then over rev while coasting down the other side. In that scenario shorting the pot box would not help but a buzzer could.
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How to feed an original tachometer?

Post by evric » Sat, 18 Apr 2009, 04:54

In an electric car you don't use low gear to get up hills - as I understand it. You just don't want it to go over 6000rpm (may change for each motor) at all.
Put a buzzer on it as well - good idea.
Last edited by evric on Fri, 17 Apr 2009, 18:57, edited 1 time in total.
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How to feed an original tachometer?

Post by Peter C in Canberra » Sat, 18 Apr 2009, 05:12

I guess I don't yet know in practice. On one hand I have been told I could expect to start and drive around in 3rd all the time. On the other hand I have heard the comment that one might occasionaly want to start off in 2nd with a load up a hill, or even all the time. It's not so much that you couldn't do it in 3rd but the current gets very high and a start in 2nd might be brisker and more efficient.   So I've heard. I'll have stronger opinions when I have been watching the current meter in practice some time soon.
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How to feed an original tachometer?

Post by coulomb » Sat, 18 Apr 2009, 05:50

evric wrote: In an electric car you don't use low gear to get up hills - as I understand it. You just don't want it to go over 6000rpm (may change for each motor) at all.

Well, the "change up a gear to get more torque" is a DC motor thing. For AC industrial conversions (where the maximum motor speed is comparable to the original ICE's), you would use the gearbox much more like you use it in an ICE. So you may well change down a gear to get up a hill in an electric car, though you may well find you need to change down a gear less often.

For AC with a for-EV motor, well you don't even have a gearbox, or you stay in one gear most of the time, since the motor can rev out to 11,000 or more RPM with decent torque. Though if you have the gearbox anyway (e.g. most front wheel drive conversions), you could probably get more power at high speed using a higher gear.

As I understand it.
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How to feed an original tachometer?

Post by Peter C in Canberra » Thu, 11 Jun 2009, 14:23

Dear All,
I am happy to report that the circuit posted above by Evric has been tested in my Charade and works.
NB. I have the tacho feed in part only, not the rev limiter part. My original tacho now shows revs which is much nicer looking than a needle that sulks pointing sullenly at the zero.
Thank you for your help.
Peter.
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How to feed an original tachometer?

Post by evric » Thu, 09 Jul 2009, 06:01

Peter,
What shape did you make the slotted disc for interupting the hall effect device? Can you post a picture or photo?
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How to feed an original tachometer?

Post by Peter C in Canberra » Sat, 11 Jul 2009, 20:42

Hi,
I've been trying to upload a picture but it won't go for some reason, even when I cut it down to only 40kb. I'll try to email it to you instead.
Peter
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How to feed an original tachometer?

Post by coulomb » Sat, 11 Jul 2009, 23:18

Peter C in Canberra wrote: Hi,
I've been trying to upload a picture but it won't go for some reason, even when I cut it down to only 40kb.


Peter,

not wishing to pick on you or anything, but you don't seem to be the only one with that problem. Perhaps this post will help.
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How to feed an original tachometer?

Post by a4x4kiwi » Sun, 12 Jul 2009, 01:01

I found in that in the Hilux I needed a 24v pulse trough a 1k resistor

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