Best DC controller for a 6 volt coreless motor

[hayfield]

I have bought some 6 volt coreless motors, which is the best DC controller for these motors, I think my test H&M controller may damage them?

 

Thanks

[Barclay]

H&Ms usually give at least 13v so you would have to be careful. Then again you would have to be careful with any model railway controller. I recently got one of these cheap DC motor controllers from ebay and it has the useful feature of being able to limit the maximum output. You can also adjust the PWM frequency which might help it work better with a coreless motor.

 

Edited August 6, 2021 by Barclay

[AndyID]

You could make your own using a LM317 regulator fed from a 12V DC power supply. It requires very few components. The output will be smooth DC which is best for coreless motors.

[hayfield]

10 hours ago, AndyID said:

You could make your own using a LM317 regulator fed from a 12V DC power supply. It requires very few components. The output will be smooth DC which is best for coreless motors.

 

Way over my pat grade. All I want is an easy to use test controller for DC use

[DCB]

On 06/08/2021 at 12:24, hayfield said:

I have bought some 6 volt coreless motors, which is the best DC controller for these motors, I think my test H&M controller may damage them?

 

Thanks

 H&M controllers come in two varieties, resistance units like Duettes which deliver about 16 -21 volts off load on minimum speed which and some older ones are auto transformers "Variable Transformers" which deliver about 5 volts on minimum power off load and indeed with quite a lot of load.   They will all damage the 6 volt motors f you turn he knob too far towards full speed but the older ones can't control 6 volt motors going almost to full power as soon as the knob is moved.

I would use a Morley, they deliver an increase in voltage as you turn the knob from around 1 volt  up to 16 volts off load and if you avoid high power settings your 6 volt coreless should be fine, They can run everything from 1950s H/D to modern coreless motors with impunity and don't make locos buzz like angry bees.

[hayfield]

My test controller is a safety Minor with a variable wave slider on top, is it using it at maximum that's the issue ? will using it on the lowest setting safe please 

[MJI]

7 hours ago, hayfield said:

My test controller is a safety Minor with a variable wave slider on top, is it using it at maximum that's the issue ? will using it on the lowest setting safe please 

 

 

Keep on full wave, not sure if the motors would like pulse, and don't go over half knob, also consider 2 motors in serial.

 

I have been able to control a RG4 on a Safety Minor.

 

If you have a mult meter connect to the output and mark on front where 6v is, they don't voltage drop.

[AndyID]

On 08/08/2021 at 00:39, hayfield said:

My test controller is a safety Minor with a variable wave slider on top, is it using it at maximum that's the issue ? will using it on the lowest setting safe please 

 

Hi John,

 

One thing you might do is try running them under load on pure DC versus the H&M and see if it makes any difference in terms of power output and heating. A good source for pure DC is batteries. A few AA batteries in series should work quite well.

 

If you prefer the results with batteries you should try to get a variable PSU with a smooth DC output. If you can't find one you could easily make one from a few components. It's a lot easier than building turnouts and we can walk you through it.

 

Cheers,

Andy

[hayfield]

9 hours ago, AndyID said:

 

Hi John,

 

One thing you might do is try running them under load on pure DC versus the H&M and see if it makes any difference in terms of power output and heating. A good source for pure DC is batteries. A few AA batteries in series should work quite well.

 

If you prefer the results with batteries you should try to get a variable PSU with a smooth DC output. If you can't find one you could easily make one from a few components. It's a lot easier than building turnouts and we can walk you through it.

 

Cheers,

Andy

Andy

 

Thanks but you lost me at the PSU quote. 

 

All I want is a good inexpensive controller.

[DCB]

The 

On 08/08/2021 at 08:39, hayfield said:

My test controller is a safety Minor with a variable wave slider on top, is it using it at maximum that's the issue ? will using it on the lowest setting safe please 

My safety minor  has a minimum voltage of around 3,5 off load which while find for most "12volt" OO loco will mean next to no controllability with 6 volt motors.. I make up a voltage reducer out of diodes that's pairs of diodes in inverse parallel, between output and track. At about 0.7 volts per diode , for around 0 volts minimum power (as opposed to "Off")  maybe try six pairs ( that's 12 total) They give a relatively constant voltage drop across a wide range of loadings 1N100 I think is the bog standard 1 amp one, I bought 100 for about 2 quid years ago from Maplin and still have most of them, but I use 11 diodes around a 12 way switch as a controller which works very well if you can live with 11 notches.  An N gauge  Morley is probably a better bet if you have a spare arm or leg you no longer need.

[kevinlms]

Question for you, John. The simplest way of testing these motors would be a diode controller as described by David Broad (under his new alias!)

 

The question is, once you built a model with a 6 Volt motor, how are you going to prevent yourself accidentally connecting a 12 volt controller to that loco? That seems to me, a major drawback to using a 6 volt motor in a particular model, if everything else is 12 volts.

 

It is an advantage of DCC, where you can adjust the decoder settings, thus allowing a loco to run on the standard set up, because the adjustments are done inside the loco. But I doubt you have any intention of going DCC, to overcome this problem.

[Izzy]

Maybe I am looking at this wrong, but I would have thought that simply adding a suitable sized resistor to the 6v coreless motor/s feed would be easier, then it wouldn’t much matter what nominally 12v controller you used. Nigel Lawton supplies 6v coreless micro motors and provides dropping resistors for use with a 12v nominal supply. He suggests around 150ohms is about right. Online ohms calculators suggest anything from about 25ohms up to 50ohms depending on input voltage and current draw so a bit of experimenting may be needed. 

[DCB]

 

1 hour ago, Izzy said:

Maybe I am looking at this wrong, but I would have thought that simply adding a suitable sized resistor to the 6v coreless motor/s feed would be easier, then it wouldn’t much matter what nominally 12v controller you used. Nigel Lawton supplies 6v coreless micro motors and provides dropping resistors for use with a 12v nominal supply. He suggests around 150ohms is about right. Online ohms calculators suggest anything from about 25ohms up to 50ohms depending on input voltage and current draw so a bit of experimenting may be needed. 

 

Resistors are good with variable resistance controllers, Duettes and the like and PWM controllers but you lose controllability on variable voltage. Variable voltage literally alter the voltage as you move the knob and the load varies the amps, you get a near constant reading on the voltmeter and near constant speed whether off load or pulling 1 amp.  I don't know how seriously a resistor would affect things in this scenario but if you must use a resistor use one rated for at least an amp and keep it well ventilated.  My experience in the motor trade is resistors are a total PITA and best avoided.

 

[AndyID]

A perfect DC motor would have no internal resistance. Its speed would be determined only by the applied voltage and the speed would remain constant for any applied voltage even when the load on the motor was changing. The motor would draw more current or less current as the load increased or decreased but the speed would be unaffected.

 

But obviously motors are not perfect. The windings have resistance as do carbon brushes. As the load on the motor increases the current tends to increase and more of the applied voltage is dropped (lost) across the internal resistance. Consequently the motor is not "seeing" the full applied voltage and because of that it slows down.

 

That's why it's much better to feed DC motors from a well regulated power supply. A resistance controller cannot supply the motor with constant voltage under variable load because the voltage drop across the controller's resistance increases as the load increases (which is the exact opposite of what you'd want to happen.) It also accounts for why model locos tend to do jack-rabbit starts when powered from a resistance controller.

 

It's possible to make a regulated DC controller that compensates for the motor's internal resistance by increasing the voltage as the current increases but they only work properly if the power distribution to the track is really good.

 

Sorry for the long explanation

 

 

 

Edited August 26, 2021 by AndyID
extra word