Wiring of Turnigy Watt Meter with external shunt

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ScooterDude17
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Wiring of Turnigy Watt Meter with external shunt

Post by ScooterDude17 » Dec 17, 2017 8:03 pm

Hi Forum:

I have an e-max electric scooter I equipped with a Turnigy 130A Watt Meter, which I connected to an external shunt (instead of using the one that the Turnigy came with). I also added a push button switch (to one of the 2 red wires) to be able to reset the Turnigy. It seems, though, that I didn't quite get the wiring right ... :(.

I attached the 2 red wires of the Turnigy to the 2 low amp connectors of the external shunt, the 2 black wires of the internal shunt of the Turnigy are not connected.

However, the display remains dark even when everything else works just fine. Only when I connect the + and - pins on the side of the Turnigy to a 12V source the display comes on. But still no data :evil:!

Thanks!

ScooterDude17

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Re: Wiring of Turnigy Watt Meter with external shunt

Post by amberwolf » Dec 18, 2017 2:42 am

Does this help?
https://endless-sphere.com/forums/viewt ... =2&t=21976
ScooterDude17 wrote:
Dec 17, 2017 8:03 pm
I attached the 2 red wires of the Turnigy to the 2 low amp connectors of the external shunt, the 2 black wires of the internal shunt of the Turnigy are not connected.
FWIW, if you don't have both a + and a - wire from the battery to the meter, the meter doesnt' get power and it doesnt' have a ground reference to make measurements from.

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Wiring of Turnigy Watt Meter with external shunt

Post by ScooterDude17 » Dec 18, 2017 9:47 pm

Hi Amberwolf:

Thanks a lot for your feedback and the link. I'll need some time to review Jeremy's post - I hope it's OK to come back with more questions in case his post doesn't resolve the issue!?

Now, this is a picture of the external shunt:
External Shunt.jpg
External Shunt.jpg (148.15 KiB) Viewed 177 times
One of the 2 thick black wires goes to the controller's minus pole, the other to the minus pole of the batteries. And the 2 thinner red wires (in between the black cables and one above the other) are connected to the 2 red wires of the Turnigy.

Now, as far as I understand, shunts usually get looped into the minus (grounded) side of the electric circuit. As for the red wire soldered to the smaller yellow circuit board of the Turnigy (and which is connected to the low amp connectors of the external shunt) is actually one wire that's stripped of its insulation at the point where its soldered to the yellow circuit board. Then there are the + and - pins on the side of the Turnigy. To me that seems like a total of 5 wires. Last but not least, it almost sounds like I'll definitely have to remove the internal shunt of the Turnigy?!

I'm sorry if I'm a bit dense here, but how do I have to wire the Turnigy in order to get it to display measurements?!
1) How can I connect the Turnigy (it's black wires) to the external shunt without needing to run the heavy battery/controller leads up to the Turnigy? Woudn't that be the - part of the shunt circuit?
2) Can I connect the red wire of the Turnigy to the shunt's 2 low amp connectors and the reducer's +12V (I put in a 48V/12V reducer to run everything that requires 12V), which would be the + part of the shunt circuit?! Or....
3) Would I in any case need the + and - pins on the side of the Turnigy connected to +12V and -12V of the 48V/12V reducer? But then, what about the red wire in 2)?!

Again, I'm really sorry for being really slow here. But electric circuits just aren't my thing :oops:.

Thanks so much.

ScooterDude17

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Re: Wiring of Turnigy Watt Meter with external shunt

Post by major » Dec 19, 2017 8:46 am

ScooterDude17 wrote:
Dec 18, 2017 9:47 pm

Now, this is a picture of the external shunt: External Shunt.jpg One of the 2 thick black wires goes to the controller's minus pole, the other to the minus pole of the batteries. And the 2 thinner red wires (in between the black cables and one above the other) are connected to the 2 red wires of the Turnigy.
Hi Dude,

Something is out of whack. That looks like no shunt I've ever seen. Where did it come from? And is that power lead (thicker black wire) attached with a nylon screw? That would be a fire waiting to happen. Please post more info about that "external shunt".

But that is academic because you pretty much need to use the original meter shunt and relocate it remotely like Jeremey describes in the reference amberwolf supplied. It also appears you would benefit from increasing your understanding of basic "meter shunt" or "current shunt". Try a google on those terms.

Regards,

major
Last edited by major on Dec 19, 2017 3:55 pm, edited 1 time in total.

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Re: Wiring of Turnigy Watt Meter with external shunt

Post by amberwolf » Dec 19, 2017 2:01 pm

Yes, you need to go to that thread, and follow those instructions to use an external shunt. If you don't use the original (unmounted and then used externally) then the meter won't read correctly, unless you calibrate your new external shunt to be *exactly* the same resistance as the original.

If it's already close but too low, you might be able to do it by shaving bits of it off in extremely small amounts until it matches, but these are extremely low resistances so it'll take precision measurements to be sure it's right. (or repeatedly comparing readings you get with the original shunt vs readings iwth the new one, using a constant current source precisely set to one value for all testing, as you calibrate the new shunt).

If it's too high a resistance already, there's no good way to precisely correct that. There are electronic circuits you can build (see some of Jeremy Harris's other threads/posts about shunts), but it's easier to just use the original.


FWIW, I'd guess that shunt is an aluminum "heatsink" with a PCB sandwiched onto the backside taht we can't see, with the actual shunt on that invisible side. Suspect the nylon screws/etc are meant to secure the unit as a whole to whatever other surface it's meant to go on (heatsink?) while insulating electrical connection from that surface (assuming thermal pad between them).

Guessing that the thick power wire we can see is attached on the wrong side, if so, and ought to be bolted on with metal bolt/nut (other one as well).

I don't know what the smaller wire connections are like; I cant' clearly see them in the pic (whited out), but it looks like spade lugs. Probably an "ok" connection for low-current/low-voltage readout to the wattmeter.

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Wiring of Turnigy Watt Meter with external shunt

Post by ScooterDude17 » Dec 20, 2017 10:47 pm

Hi Amberwolf and Major:

Thanks so much for your feedback :D and sorry about my latish reply!

As for that 'weird shunt', the fact, that I'm more into mechanical than electrical stuff and that I was already rather busy fixing up my electric scooter I guess I relied on advice I probably shouldn't have :oops:. And the guy who sent me the link to that shunt sounded like he knew what he was talking about. How he found out about where to get it I have no idea.

Well, all things considered it seems like a very good idea to make use of that internal Turnigy shunt after all and ditch the other one. The "Mounting Turnigy Watt Meter" thread plus another one on the same topic I found on a German e-scooter forum (I do speak German fairly well) should help me to get the job done. And taking up your advice, Major, I've found a couple of websites with info on electic shunts I'm going to read up on over the next couple of days.

Hopefully, if there are still some issues I have a problem with :?, I can post a few more questions.

Many thanks again.

ScooterDude17 aka John

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