Will this wiring work please: rolling road, voltmeter, ammeter, additional tracks?

[flockandroll]

Hi. 

Will the attached wiring plan work please for DC? A rolling road with analogue voltmeter and ammeter, with additional tracks, on a 1 foot x 3 foot board? The idea of the switches is so that I can switch between rolling road and the other tracks (with future provision for DCC). Thanks

[Compound2632]

There's rather more switches than you need. Just one simple switch for each of the three circuits, say on the red side (could be either) would be quite enough, for DC.

[DCB]

Why so many connections to the rails?   Track comes in 36" or 39" lengths.  You only need one red and one black wire per 3ft length.  It's very bad practice to make 3ft sections up  from lots of shorter lengths.  Fishplates are the enemy of continuity.

Connecting black to all 3 tracks and switching red is a lot neater especially if you use a single rotary selector switch.  ( or connect red and switch black )

[RAF96]

I would have thought the ammeter and voltmeter needed to be in the common line from the controller.

[Compound2632]

12 minutes ago, RAF96 said:

I would have thought the ammeter and voltmeter needed to be in the common line from the controller.

 

The voltmeter is correctly drawn in parallel with the rolling road and the ammeter in series with it. As I read the OP, these diagnostics are only wanted for the rolling road, not the other two test tracks. 

[AndyID]

Do the meters handle voltage and current in both directions?

[flockandroll]

20 hours ago, Compound2632 said:

There's rather more switches than you need. Just one simple switch for each of the three circuits, say on the red side (could be either) would be quite enough, for DC.

I was thinking of using double pole switches, I want to make double sure the rolling road is isolated from the other tracks as in the future I intend it to also be a DCC programming track.

[flockandroll]

17 hours ago, DCB said:

Why so many connections to the rails?   Track comes in 36" or 39" lengths.  You only need one red and one black wire per 3ft length.  It's very bad practice to make 3ft sections up  from lots of shorter lengths.  Fishplates are the enemy of continuity.

Connecting black to all 3 tracks and switching red is a lot neater especially if you use a single rotary selector switch.  ( or connect red and switch black )

Yes, I think I was over zealous with the rail connections / droppers.

That is a good suggestion about a rotary switch. (But (I know this is the non-DCC forum) I want it to in the future also be usable on DCC). I was struggling to find (or looking in the wrong places) a rotary switch that was rated at over 0.5 amps with a matching knob that was a few pounds.

[flockandroll]

9 hours ago, Compound2632 said:

 

The voltmeter is correctly drawn in parallel with the rolling road and the ammeter in series with it. As I read the OP, these diagnostics are only wanted for the rolling road, not the other two test tracks. 

Yes. Tracks 2 and 3 are for me to practice track laying, ballasting, clearances, and what to do about the RTR couplings

[flockandroll]

48 minutes ago, AndyID said:

Do the meters handle voltage and current in both directions?

That is a very good point!

Testing the ammeter with a battery, one way round the needle is hard against the stops,..! Oh dear! I guess it needed one that read  zero at the centre! And the voltmeter will be similar...Is there a wiring way round this?

[Crosland]

For the ammeter, connect the ~ pins of a bridge rectifier in the feed to the rolling road and connect the meter across the + and - terminals. Current will always flow the same direction through the meter, regardless of the supply polarity. The voltage to the rolling road will be reduced by two diode drops.

 

For the voltmeter use another bridge rectifier with the ~ terminals connected to the feed and return of the rolling road. Connect the meter across the + and - terminals. Again, you will need to allow for two diode voltage drops when measuring the voltage.

 

[AndyID]

2 hours ago, flockandroll said:

That is a very good point!

Testing the ammeter with a battery, one way round the needle is hard against the stops,..! Oh dear! I guess it needed one that read  zero at the centre! And the voltmeter will be similar...Is there a wiring way round this?

 

Yes, you could add a four pole switch that reverses their polarities.

[AndyID]

Another way to do it is to always set the controller in one direction when you are using the rolling road. Put the voltmeter across the controller output and the ammeter in series with one feed then connect that to a two pole switch wired to be able to reverse the polarity to the rolling road. It might be useful if it also has a center off position.

 

You would still need to be able to disconnect the voltmeter when the controller is running in normal mode but you only need a single-pole off-on switch to do that.

 

[DCB]

Good point about Ammeter and Voltmeter, I didn't factor that in, too used to digital ones which are reversible! 

For DCC I would stick with 1 amp switches but put a 1 amp polyfuse in circuit as an overload cut out. 

[AndyID]

Here' a sketch.

 

 

 

[Compound2632]

I'm finding all this unnecessarily complicated. What's wrong with getting a bag of 4 mm banana plugs and sockets and doing the switching by hand? including switching the polarity on the ammeter?

[AndyID]

4 hours ago, Compound2632 said:

I'm finding all this unnecessarily complicated. What's wrong with getting a bag of 4 mm banana plugs and sockets and doing the switching by hand? including switching the polarity on the ammeter?

 

But then I wouldn't be able to demonstrate my superior drawing skill 😄

[AndyID]

10 hours ago, Compound2632 said:

I'm finding all this unnecessarily complicated. What's wrong with getting a bag of 4 mm banana plugs and sockets and doing the switching by hand? including switching the polarity on the ammeter?

 

Being a bit more serious (which admittedly I do struggle with) the OP did ask a reasonable question. You are quite correct in saying it's not difficult to set this up with jumpers and a bread-board for people who have a good handle on electric circuits but a great many people really do not. My take on it is the OP is willing to learn and anything I can do that helps clarify things for the OP is worth a little effort on my part.

[Compound2632]

2 hours ago, AndyID said:

My take on it is the OP is willing to learn and anything I can do that helps clarify things for the OP is worth a little effort on my part.

 

Yes indeed. There's a world of possibilities, from chocolate blocks (the plug-in type would be effective here):

 

 

... to PCB-mounted solid state switches, controlled via a mobile phone interface. 

 

I know where I sit on that scale!

[flockandroll]

I want a rolling road because the locomotives need to run, and I don't yet have a layout, plus it should be good practice / skill building for me. And I want to enjoy using it.

 

So I very much agree with Compound2632, "I'm finding all this unnecessarily complicated"

 

The main reason for adding the meters was to increase the 'play value' so simple to use is the way to go.

 

Taking all comments on board, I am thinking for the ammeter, just to get a different analog one that is centre zero. And for the voltmeter, could I use a double pole double throw switch wired so as to, when the polarity to/from the voltmeter has changed due to the controller reversing direction, change it back? Could the voltmeter be damaged if I forgot, and it gets 12 volts 'in the wrong dirsction' pushing the needle against the stops for say 5 minutes? Could a diode be put in the circuit next to the voltmeter to stop this?

I will try to post my attempt at a circuit diagram for this tomorrow.

 

Thanks 

 

(So far only found  one type of centre zero voltmeter, a 100v - 0 - 100v model! But plenty of ammeter versions.

And for the "play value" I wanted analogue meters not digital)

 

[cliff park]

You could of course put a bridge rectifier in the voltmeter circuit. Then it wouldn't matter which way round the supply was . But you would lose a volt or so across the diodes, just have to add a bit on to the readings.

[Crosland]

4 hours ago, cliff park said:

You could of course put a bridge rectifier in the voltmeter circuit. 

I think I suggested that on Sunday!

 

You can do something similar for the ammeter.

[flockandroll]

Good point, I will look into that also. I only know of the name, not how they work. 

[kevinlms]

On 04/05/2022 at 08:32, flockandroll said:

I want a rolling road because the locomotives need to run, and I don't yet have a layout, plus it should be good practice / skill building for me. And I want to enjoy using it.

 

So I very much agree with Compound2632, "I'm finding all this unnecessarily complicated"

 

The main reason for adding the meters was to increase the 'play value' so simple to use is the way to go.

 

Taking all comments on board, I am thinking for the ammeter, just to get a different analog one that is centre zero. And for the voltmeter, could I use a double pole double throw switch wired so as to, when the polarity to/from the voltmeter has changed due to the controller reversing direction, change it back? Could the voltmeter be damaged if I forgot, and it gets 12 volts 'in the wrong dirsction' pushing the needle against the stops for say 5 minutes? Could a diode be put in the circuit next to the voltmeter to stop this?

I will try to post my attempt at a circuit diagram for this tomorrow.

 

Thanks 

 

(So far only found  one type of centre zero voltmeter, a 100v - 0 - 100v model! But plenty of ammeter versions.

And for the "play value" I wanted analogue meters not digital)

 

 

Centre zero meters are always going to be an issue, due to availability and also price. 

[kevinlms]

On 04/05/2022 at 08:32, flockandroll said:

I want a rolling road because the locomotives need to run, and I don't yet have a layout, plus it should be good practice / skill building for me. And I want to enjoy using it.

 

So I very much agree with Compound2632, "I'm finding all this unnecessarily complicated"

 

The main reason for adding the meters was to increase the 'play value' so simple to use is the way to go.

 

Taking all comments on board, I am thinking for the ammeter, just to get a different analog one that is centre zero. And for the voltmeter, could I use a double pole double throw switch wired so as to, when the polarity to/from the voltmeter has changed due to the controller reversing direction, change it back? Could the voltmeter be damaged if I forgot, and it gets 12 volts 'in the wrong dirsction' pushing the needle against the stops for say 5 minutes? Could a diode be put in the circuit next to the voltmeter to stop this?

I will try to post my attempt at a circuit diagram for this tomorrow.

 

Thanks 

 

(So far only found  one type of centre zero voltmeter, a 100v - 0 - 100v model! But plenty of ammeter versions.

And for the "play value" I wanted analogue meters not digital)

 

 

It is a bit complicated,  because the task of accurately measuring voltage and current on a varying DC circuit isn't really simple.

 

I suggest that you chose an easy to use solution,  rather than an easy to wire solution. Andy's version is long term easy as you only need to do the job once, then it's foolproof.