What Voltage?

[Metr0Land]

For many years I've used my faithful H&M Duette, without the need for a multi-meter.  You can see the low tech tester that I use.  If it lights up, I have a connection - simples.

 

 

As part of the infrastructure for my new layout I bought a cheap multimeter  When trying it on a piece of test track it shows 15+ volts DC with the knob only turned half way up.

 

Should I be worried, or could it be the multimeter is faulty as I've no way of calibrating it?   Or is it a case that a '12v' controller actually delivers 15v? 

[Adrian Wintle]

For many years I've used my faithful H&M Duette, without the need for a multi-meter.  You can see the low tech tester that I use.  If it lights up, I have a connection - simples.

 

 

As part of the infrastructure for my new layout I bought a cheap multimeter  When trying it on a piece of test track it shows 15+ volts DC with the knob only turned half way up.

 

Should I be worried, or could it be the multimeter is faulty as I've no way of calibrating it?   Or is it a case that a '12v' controller actually delivers 15v? 

 

The multimeter is probably ok. It is much more likely that the '12V' controller produces more than 12V, particularly if there is no load. Try measuring again with a loco on the track.

 

Adrian

[34theletterbetweenB&D]

The nominal 12V output is what the controller ought to be able to maintain on the rails, up to the maximum current it is rated for. Further to what Adrian has already posted, when neglible current is drawn, the voltage you will see is whatever the transformer secondary stands at, with very small losses. Put the bulb across the track, and see the track voltage reduce.

 

Look at that Duette. How old is it? Looks like it was manufactured yesterday...

[Metr0Land]

Thanks for the replies guys.  The Duette was late 70s/early 80s though didn't get much use until about 8 years ago.

[Silver Sidelines]

Nice looking controller

 

You can tell it has not had much use because the dials around the knobs have not lost all their paint.

 

 

 

..  Or is it a case that a '12v' controller actually delivers 15v? 

I had one for over ten years until the rheostats wore out.

 

Regards

 

Ray

[DCB]

This is quite normal for a resistance type controller, 12 volts means 12 volts in a computer, 14 in a car battery charger and 19 or more in a resistance controller.  This is no real problem, apart form iffy slow running the real downside being a tendency for locos to race downhill and slow on up grades on constant speed settings and an inability to double head with locos of different chassis and motor combinations.

 

The old H and M Units, Safety Minor etc had variable transformers whereby the voltage increased with the control setting which gave much better correlation between the control knob setting and speed.  Morley and OnTrack controllers are also variable voltage and will show 2 volts when just cracked off the mid position, in fact you can run LEDs from the minimum speed setting, while the max voltage is 19 volts for the OO OnTrack and around 15 for the N gauge unit.

 

The Duette has a single transformer for two rheostats and on mine as you slowed one train the other would speed up, then a rectifier failed and it was half wave only one side..

[Metr0Land]

The Duette has a single transformer for two rheostats and on mine as you slowed one train the other would speed up, then a rectifier failed and it was half wave only one side..

 

Ah interesting I hadn't known about that.  On my old layout I only used one side as the track layout could all be controlled by one controller (and indeed I could only cope with one loco moving at a time).

 

My new layout is meant to be 2 main tracks so I'll have to keep an eye on this.  However, I had sort of made provision for a newer controller needing to be bought at some stage, so it won't be the end of the world if she's pensioned off (it's just one less loco to be purchased at today's prices).