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-   -   Best amp meter for motor setup (https://www.rctech.net/forum/radio-electronics/1049231-best-amp-meter-motor-setup.html)

Bry195 09-01-2019 08:44 PM

You have the right idea to measure current on chassis. This will help you measure current due to acceleration of the dive train and friction. What you wont be able to measure is actual current from accelerating the mass of the car. Good idea though.

Roelof 09-01-2019 11:24 PM


Originally Posted by m3rcfh (Post 15503458)
I was just curious about how you would solder the bullets into the thin wires that come with this amp meter... do I need to replace the wires by a thicker gauge?

https://cimg7.ibsrv.net/gimg/www.rct...26dfbf5c11.jpg

There is also the current shunt resistor inside that needs to stay put. That is where the current is going through, the small leads is only measuring the voltage over the shunt resistor

m3rcfh 09-02-2019 04:49 AM


Originally Posted by Roelof (Post 15503725)
There is also the current shunt resistor inside that needs to stay put. That is where the current is going through, the small leads is only measuring the voltage over the shunt resistor

Got it, I thought people were getting rid of the fuse circuit and soldering the connector directly into the red/black wire, just keeping the shunt resistor connected between positive and negative. That way you wouldn't need a fuse to make it work.

Is there a specific size of fuse I should use? Or a 30A will be fine?

m3rcfh 09-02-2019 04:50 AM


Originally Posted by Bry195 (Post 15503672)
You have the right idea to measure current on chassis. This will help you measure current due to acceleration of the dive train and friction. What you wont be able to measure is actual current from accelerating the mass of the car. Good idea though.

Not only this will help measure current draw with the drive train friction, but also you can remove the pinion and test the amp draw free of load directly on the chassis, so you can test different amp draws without desoldering

Roelof 09-02-2019 06:23 AM

No need to use a fuse, unless you are planning to go far beyond the 30A

the rc guy 09-02-2019 07:14 AM

Use a 30 amp fuse that way you have a safety factor in your circuit

Andy Koback 09-02-2019 08:12 AM

I never tried it but I don't think it would work without the fuse.

Roelof 09-02-2019 11:23 AM


Originally Posted by Andy Koback (Post 15503839)
I never tried it but I don't think it would work without the fuse.

Explain why you would think that. A fuse is noting more than a wire that melts away when more current is going through it than specified. No fuse will work also but with a shortcut wires will glow up but then again, in a car you do not use a fuse either.....

Andy Koback 09-02-2019 11:50 AM

You would need the fuse to complete the circuit. That's why when a fuse blows, the circuit is broken. I'll have to try it sometime.

m3rcfh 09-02-2019 11:54 AM


Originally Posted by Roelof (Post 15503800)
No need to use a fuse, unless you are planning to go far beyond the 30A

Would you mind explaining? Seems like the negative leg of the fuse tester is not connected, unless you put a fuse in there

https://cimg1.ibsrv.net/gimg/www.rct...9fc2f78bdb.jpg

Roelof 09-02-2019 12:36 PM

Ah, I thought you was speaking of the use of a fuse in any type circuit, yes for that divice you need a fuse. 30A or larger will be OK.

Andy Koback 09-02-2019 01:02 PM

This piece is what I was referring to. Now that we're on the same page. -)

m3rcfh 09-02-2019 02:03 PM


Originally Posted by Roelof (Post 15503982)
Ah, I thought you was speaking of the use of a fuse in any type circuit, yes for that divice you need a fuse. 30A or larger will be OK.

Perfect, thank you!
Just had one last question, can I desolder at the fuse plates (where the purple arrows are pointing at) and just solder a piece of 12awg wire with the male/female bullet?
that way I can ditch that whole grey fuse connector and the fuse circuit, for a clean look.

Thanks again

https://cimg9.ibsrv.net/gimg/www.rct...233f47b65c.jpg

Andy Koback 09-02-2019 03:22 PM

Then you have no protection of your unit. Your still gonna have another wire coming out the side so looking cleaner...not really. This is not for concours btw. -)


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