# Tach as ammeter with the Soliton?



## dedlast (Aug 17, 2013)

steelneck said:


> It will probably need something that translates voltage to pulses. Logically i know it is possible, but i do not know how.


There a lot of options. Some easier and cheaper than others. The link is a Google images search for "voltage to frequency converter". A regular Google search has a lot of hits, too.

Bill


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## ken will (Dec 19, 2009)

steelneck said:


> In the Soliton manual there is a picture on how to connect an ammeter, i am thinking if there is a way to use this output to drive a tachometer as ammeter?
> 
> It will probably need something that translates voltage to pulses. Logically i know it is possible, but i do not know how. In my conversion i was originally going to use the Zeva Fuel gauge driver that also had output to drive a tach as ammeter. So i bought a 0-10K RPM tach, to be used both as a normal tach and ammeter. I never got the fuel gauge driver to work with my tank meter, i am now replacing it with an E-Xpert pro. But now i lost the FGD function of driving the tach as ammeter. I really would like to have that feature back and the Soliton have the option to output both battery amps and motor amps, but not in the right "format" for a tachometer.
> 
> Any idea how to "translate" the Soliton amp-output to drive a tach?


An Ammeter is a voltmeter with a shunt.
A Tachometer is a voltmeter driven by a frequency to voltage circuit.
If you use just the voltmeter part of the Tachometer and the correct shunt you will have an Ammeter.


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## Tesseract (Sep 27, 2008)

steelneck said:


> ...
> It will probably need something that translates voltage to pulses. Logically i know it is possible, but i do not know how.


Unfortunately, no, you can't directly drive a tachometer with any of the "gauge driver" outputs on the Soliton. The reason why is that that Soliton uses PWM of a fixed frequency square wave to represent a variable DC voltage on a gauge driver output - same as it does to vary motor current. A tachometer translates *frequency* into RPM, and cares little about the duty cycle, per se.

In other words, you will always get the same reading on the tachometer when connected to a gauge driver output.

And doubly unfortunately, we will not add the ability to do this in the Soliton firmware for the same reason we removed the ability to drive fuel gauges: there's too much variability in how OEM gauges operate. Indeed, this is one of the reasons why so many are unhappy with the Zeva product.

Use the OEM tachometer to read RPM as it was intended, is my suggestion.


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## steelneck (Apr 19, 2013)

ken will said:


> If you use just the voltmeter part of the Tachometer and the correct shunt you will have an Ammeter.


I know, thing is that i still want to use the same tach as a regular tach, with the zeva FGD i could use it as ammeter too, just a switch choosing wich way i wanted it to work.



Tesseract said:


> Unfortunately, no, you can't directly drive a tachometer with any of the "gauge driver" outputs on the Soliton.


I know, that is is why i am asking if anyone know how to translate voltage into frequency.



Tesseract said:


> Use the OEM tachometer to read RPM as it was intended, is my suggestion.


Yes i will, but that does not exclude the other use, just a switch to chose. This is how it was set up until now. Yes, i could just keep the FGD and just use it to drive the tach as ammeter, for the moment i probably will, but it would probably be a much cleaner solution with a "translator" for the Soliton output and with that i can even chose between battery and motor amps.



dedlast said:


> There a lot of options. Some easier and cheaper than others. The link is a Google images search for "voltage to frequency converter". A regular Google search has a lot of hits, too.


Thanks, you did probably anwer my question. But yur answer was a bit over my head, i am a mechanic, though i do know how to solder things, but i need to know a bit more precise what pieces to solder together..

EDIT: Google seem to get the image search backwards, all hits seem to be "frequency to voltage" not the other way around. But since google nowadays customize all searches to what they think you are searching for (they have lost their soul long ago), you and i wont get the same results using the same search words.


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## ken will (Dec 19, 2009)

If you live near Malmo you might ask these people.

http://local.arduino.cc/malmo/about-us/


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## Tesseract (Sep 27, 2008)

steelneck said:


> I know, that is is why i am asking if anyone know how to translate voltage into frequency.


Sure - the LM331 is an oldie but a goodie IC that performs this function. Searching for "V/F converter" or "VCO" will also get you results.

Mind you, this is still what I would call a kludge because you have to average the digital PWM output of the Soliton into a variable DC voltage then convert that back into a variable frequency. Messy.



steelneck said:


> ... but it would probably be a much cleaner solution with a "translator" for the Soliton output and with that i can even chose between battery and motor amps.


No way to select between battery and motor amps on a single gauge driver output without accessing the web interface. A much better solution would be to use an Arduino or the like to extract the motor current and duty cycle information from the logging data constantly streamed to the ethernet port on the Soliton.


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## steelneck (Apr 19, 2013)

Tesseract said:


> Sure - the LM331 is an oldie but a goodie IC that performs this function. Searching for "V/F converter" or "VCO" will also get you results.


Thanks, that LM331 looks to do it. Now i have to figure out how to get it to make 0-12V (or whatever the Soliton output is) into something like 0-333Hz. 



Tesseract said:


> Mind you, this is still what I would call a kludge because you have to average the digital PWM output of the Soliton into a variable DC voltage then convert that back into a variable frequency. Messy.


I cannot think of a simpler solution, It will not be exact, but good enough. I could very well just have the TBS E-Xpert. This is not something important, just a bit of fun-factor.



Tesseract said:


> ... use an Arduino or the like to extract the motor current and duty cycle information from the logging data constantly streamed to the ethernet port on the Soliton.


A whole computer as interface just to turn a needle on a dial! Hardly what i would call KISS.


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## ken will (Dec 19, 2009)

steelneck said:


> A whole computer as interface just to turn a needle on a dial! Hardly what i would call KISS.


Well, I would not call an Arduino a Whole computer!

To keep it *looking* simple you could use just the Tach-meter as your only display. 

The Arduino can drive the single meter with...RPM, battery amps,motor amps,battery voltage,motor voltage, motor temperature, controller temp, atmospheric temp, Humidity, MPH.,Trip time, SOC, your pulse rate, etc.


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## arklan (Dec 10, 2012)

http://zeva.com.au/index.php?product=103
this will do what u ask im sure


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## steelneck (Apr 19, 2013)

arklan said:


> http://zeva.com.au/index.php?product=103
> this will do what u ask im sure


If you read this discussion you would have seen that i have one of those. Yes the the ammeter-driving function works, sort of, but not the fuel gauge driver part that did not work with any of my fuel gauges. I also wrote that i will probably keep it for the moment, to drive the tach as ammeter. But now to the "sort of" part that i learned recently. At low amps, it seem show at least 50% less than the readings i get from the Soliton. But if i floor it it reads the same as the Soliton. So, not even the ammeter driving part seem to work as advertised.


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## bwjunkie (Jul 31, 2013)

I feel this question will be shot down fast, lol:
Shouldn't there be a way to infer the RPM just from the EMI / WhiteNoise / RF energy coming from a spinning motor?

josh


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## steelneck (Apr 19, 2013)

bwjunkie said:


> Shouldn't there be a way to infer the RPM just from the EMI / WhiteNoise / RF energy coming from a spinning motor?


This is about using an ordinary tach as ammeter. The Soliton controller already have output to drive a tach as it is intended to be used. My question is how to translate the Soliton ammeter output voltage into a frequency readable by a tachometer.


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## piotrsko (Dec 9, 2007)

Ok I'm dumb and might have missed it: on the OTHER side of the lm331 (?) inside the tach Should be a plain old 50 micro amp meter movement powered by a set of 2 leads. Most of the cars I work upon have replaceable components that are accessible.

No I'm not, somebody said this on last page


Use 
VOM meter theory for the resistive network shunt, bypass the internal F to V circuit.


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## steelneck (Apr 19, 2013)

piotrsko said:


> Ok I'm dumb and might have missed it:


Nahh.. Recently i read a funny thing on a friends T-shirt: "I am not dumb, i just have a bit of unluck when i think"

Yes. the idea to bypass most things inside the tach is a good one. I may look into that. It may even be possible to fix with just two resistors as voltage divider.


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## urumqix (Jan 31, 2017)

steelneck said:


> Nahh.. Recently i read a funny thing on a friends T-shirt: "I am not dumb, i just have a bit of unluck when i think"
> 
> Yes. the idea to bypass most things inside the tach is a good one. I may look into that. It may even be possible to fix with just two resistors as voltage divider.


How did the bypass solution go? I'm having the same needs as yours: to get the beautiful KOSO RX2N+ Meter work with my BWSX electric scooter.


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