Wiring up Voltmeter + Ammeter

[eSCHEn]

Got a voltmeter + ammeter combo off eBay but it's a three wire rather than five wire system. I cannot get sense out of this thing. Would some kind soul do me a simple wiring diagram? I have a 50A 75mV shunt but you can use without for low loads. I'm testing with 12V and a 5W bulb.

Pictures:


Any help appreciated, this one is doing my head in.

 

[the snooper]

surely 2 of them power it and produce the voltage reading then the 3rd for amperage

 

[the snooper]

 

[The_Yellow_Ardvark]

One is the common line. (neg) the other 2 are for current, wired in series, the other for the volts, wired in parallel.
I am asking my sparky fiends what is what.

 

[eSCHEn]

Cheers chaps. @Snooper - yeah that's the first image I get from Google as well but transposing those colours, even allowing for inverting, gets nothing of sense when I verify with multimeter.

 

[the snooper]

does it have reverse polarity protection ? if so you should be able to confirm + & - via the diode

 

[eSCHEn]

No identifiable polarity components as they're teeny smd. Even with my x20 loupe nowt. There is an electrolytic cap on the back but the traces go under a few large ICs and the segment displays so you lose them

I don't have the same unit as thatchap in the video Mr Fluffy, Mine's missing the power for the unit connector (two pin one). Wiring up the remaining plug the same (position for position as my colours are different) give me a lit bulb but a dead display.

Hmm. That board has two un-filled holes for a connector. I wonder if I can stick one in... off to check component box...

 

[steviec_lj]

Ooooo now that looks interesting!

I wonder if I'd be able to wire one up to a Sealey 170/1 for poops and laughs?

 

[the snooper]

what site did you get this from ? do you have a link

 

[eSCHEn]

Yeah, eBay: http://www.ebay.co.uk/itm/390806011207

 

[eSCHEn]

yellow is the yellow on the diagram
green is the red
blue is the black

so yellow connects to neg terminal of the bulb
blue to the batt neg
green connects to the positive of the bulb
battery to the positive of the bulb

Yup that's exactly as I have it. Bulb lights but not the display. I really do think a component hasn't been soldered where it should.

 

[AdrianH]

I use very similar to that in my CNC controller to measure the volts and current.

I would say you are missing a shunt resister.

I had to get a separate 50Amp shunt for mine, looks like you ordered a 100 Amp meter, so what it needs is a 75mV 100 Amp shunt.

Adrian

Sorry I stand corrected, if it has the pots then you should be able to adjust to an extent maybe get to 50 Amps, but I see you need to figure the colours.

Give me a min if I can help

 

[eSCHEn]

It's definitely missing a power lead, here's another listing which has got the power leads shown: http://www.ebay.co.uk/itm/281587980311

 

[eSCHEn]

Sorry @AdrianH didn't see your reply there mate. Yeah I have a shunt but you should be able to do < 10A without one.

 

[AdrianH]

There are several types mine are the 5 wire type, I take it you are going through the shunt all the time, s it is only the 10 Amp units that dont need a shunt as they have a thick wire as part of the PCB in the two holes at the end.

Going of the colours mentioned above then it would be green to pos of power supply, blue to the neg of the shunt and also a wire to the neg of the shunt to the neg of the power supply. The yellow goes to the load side of the shunt and also another wire from the load side to the load negative.

the supply to the load is another wire to the power supply +ve terminal.

Do not try to take the load through the device without a shunt, it only wants very low current through it.

Adrian

 

[AdrianH]

Sorry @AdrianH didn't see your reply there mate. Yeah I have a shunt but you should be able to do < 10A without one.

God no it cant. You have to buy one which is 10 amps manufactured

Adrian

 

[eSCHEn]

I didn't manage to try any connectors on the board last night as I was just too knackered. I'll rig up a temp supply for the display and try again tonight.

Why oh why did I not check this earlier? I've had this for months but only tested it now. Need it for Friday

 

[the snooper]

The site you bought it from has the same diagram as the one I posted look under item description

 

[AdrianH]

What are you building it into? See if the display lights with just green and blue wires. I managed to damage one of mine with ease unfortunately, but they are cheap displays at least.

Adrian

 

[eSCHEn]

The site you bought it from has the same diagram as the one I posted look under item description

Yeah I know but when wired that way it doesn't work. As the colours don't match I'm matching positions on the connector.

I will rig up power to the two unmounted pins tonight and see what happens. If it knacks it who cares - it's useless right now anyway.