Loco current consumption tester

Sapper
Posts: 64
Joined: Sat Dec 20, 2008 6:22 pm

Loco current consumption tester

Postby Sapper » Sun Dec 22, 2019 12:02 pm

Being a bit of a novice in electrics, except for very basic circuits I wonder if anyone out there could help out please. I wish to make a test unit as described in Digital Command Control for railway modellers by Nigel Burkin. He describes his test rig as such:
'My test rig consists of two panel meters fitted to an equipment box with a DPDT (centre off) switch to reverse the current so that the the meters can be used in the correct direction without having to constantly reverse the controller current. One meter is an ammeter fitted in series with the electrical circuit. The second is a voltmeter connected in parallel to the load. This also enables me to test amps versus voltage and the start voltage of a model.'

I have had a friend produce a rough sketch of the circuit (attached) which when I connect it up only showed the voltmeter working and no reaction on the ammeter. Could anyone confirm the circuit shown is correct or should it it require amendment?

Any help would be greatly appreciated.

Regards

Sapper
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nigelcliffe
Posts: 747
Joined: Mon Jul 21, 2008 8:31 am

Re: Loco current consumption tester

Postby nigelcliffe » Sun Dec 22, 2019 12:28 pm

circuit sketch is fine, but lacks details of ammeter and its performance.

So, what ammeter do you have ? ( Its possible to have one which is too low a range to see anything, or equally have one where the a typical loco would either blow the meter or any protection fuse fitted to the meter. Or have one which "works". ).

Sapper
Posts: 64
Joined: Sat Dec 20, 2008 6:22 pm

Re: Loco current consumption tester

Postby Sapper » Sun Dec 22, 2019 12:52 pm

Hello Nigel
Thanks for your quick response. The ammeter I have is a 0 - 5 Amps range and the voltmeter is 0 - 30 Volts. The ammeter reads in .2 Amps stages.

Regards

Sapper

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Tim V
Posts: 2865
Joined: Tue Jul 29, 2008 4:40 pm

Re: Loco current consumption tester

Postby Tim V » Sun Dec 22, 2019 3:57 pm

I put a bridge rectifier across the ammeter, no need for any switches. Worked fine with DCC.
Tim V
(Not all railways in Somerset went to Dorset)

nigelcliffe
Posts: 747
Joined: Mon Jul 21, 2008 8:31 am

Re: Loco current consumption tester

Postby nigelcliffe » Sun Dec 22, 2019 4:14 pm

Sapper wrote:Hello Nigel
Thanks for your quick response. The ammeter I have is a 0 - 5 Amps range and the voltmeter is 0 - 30 Volts. The ammeter reads in .2 Amps stages.

Regards

Sapper


Many motors used by S4 modellers are quite low current consumption, so 0.2A may be more than the motor is consuming.

One way to see that its all working would be to put a car side lamp bulb (old fashioned traditional bulb) on the output. Should light properly using showing about 0.5A of current on a 12v supply voltage.


- Nigel

Sapper
Posts: 64
Joined: Sat Dec 20, 2008 6:22 pm

Re: Loco current consumption tester

Postby Sapper » Fri Dec 27, 2019 2:06 pm

Gentlemen
Thanks for your input and having had another look it appears I may have been using a faulty DPDT switch as I am now getting some readings which appear to be in order.

Small 2-4-0T and 0-6-0T engines fitted with Mashima motors showing a current consumption of .2 and .3 amps respectively while an old 0-6-2T with open frame motor is showing up to .4 amps consumption which is what I would expect.

Regards

Sapper


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