Author Topic: do I need a shunt (don't answer that)  (Read 1617 times)

Offline bsa-bill

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do I need a shunt (don't answer that)
« on: 06.09. 2014 21:45 »
Quote
were getting away from gearbox's so Ill put the pics up on another thread when all the stuff arrives

We were talking digital led instruments, which have no place on a good classical A I know, but my RGF is poser and trashy with it  - soooo

the led voltmeter and ammeter arrived today - small but very bright blue displays , the volt meter works fine if at variance with my multi meter by a tenth or so.
The ammeter I'm thinking needs a bit of investigation,  in the wiring department, it has two pairs of wires (one red one black) one pair powers the display, the other pair to somehow measure the load, so far testing them on a bulb I can get the bulb to light and the ammeter display will resister 99.7, not sure what this means but pretty sure it's not amps.
I think I might need to wire in a "shunt" oh yes, now despite starting my working life as an electrician then a spell in a tv repair shop, (all a long time ago and pre transistorology) when talking about a "shunt" I am clueless, maybe a resistor of sorts.

So if any of your good selves can show me how I wire this thing in I would be mightily grateful, OTOH if you would like to point out that the present ammeter works just fine that's OK as well,  I'm also thinking along those lines but damned if I'm doing to be beat by 1 inch chunk of plastic and a Bejing techo or two
Will put up pics when I'm sure there not bits of the Doctors sonic screwdriver
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline a10gf

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Re: do I need a shunt (don't answer that)
« Reply #1 on: 06.09. 2014 22:42 »
Am thinking your amperemeter has a shunt (= resistor with very small ohm value) built in (or else it's some very special (or not complete) ammeter!). The needle (or lcd display in modern stuff) reads the very small voltage differences & variations across the shunt and shows it as amps + or -.

If what you got is a 'real' ammeter and can handle a range of + - 10 amps or so, it should do it's job just by wiring it in series, same as a Lucas in the std schematic > http://www.a7a10.net/BSA/techpics/1954%20BSA%20A-10%20Wiring.jpg


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Offline bsa-bill

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Re: do I need a shunt (don't answer that)
« Reply #2 on: 07.09. 2014 09:53 »
thanks for that e.
more testing to be done, probably with crocodile clips and spade connectors (not wires, bulb and ammeter held by fingers as so far)
I'm needing a voltmeter at least (electronic ignition) as a warning, probably wired in to the Pazon circuit so a matching Ammeter would be nice although not necessary.

here is some info on the Ammeter (the voltmeter is the same size)
 
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline muskrat

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Re: do I need a shunt (don't answer that)
« Reply #3 on: 07.09. 2014 11:37 »
G'day Bill.
I bought one of those (or similar with a volt meter switchable) a few years back for my rHonda 1100 like this one
http://www.ebay.com.au/itm/DC-120V-200A-Volt-Amp-Combo-Meter-Battery-Charge-Discharge-Indicator-With-Shunt-/171037210687?pt=AU_B_I_Electrical_Test_Equipment&hash=item27d29cb83f
I doubt if you'd need a shunt that big but would say you'd need one.
Cheers
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Offline a10gf

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Re: do I need a shunt (don't answer that)
« Reply #4 on: 07.09. 2014 11:40 »
Hello Bill, looks like it's ready to go, but IMO it will work only 'one way', 0 to 20 A. There would be place for a minus sign to the left of the digits if it where to be able to show -20 to +20. Showing charge will be fine, but am wondering what it will do when in a drain situation and current reversing, like f. ex. lights on and engine not running.

Here's an example of a +\- display.

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Offline bsa-bill

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Re: do I need a shunt (don't answer that)
« Reply #5 on: 07.09. 2014 13:55 »
yep - thanks lads, I've had another go at it, you don't need both blacks connected to get it to light up and  read but even with a headlight bulb in circuit it's 99.7
Think I've got the wrong unit, back to the drawing board, at least cheap enough to try.
Cyclone battery not living up to it's reputation though, I bought three (six volt Flash 12 volt RGF - mix and match) two are good and don't seem to lose charge, one just keeps leaking volts
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco