Speed Control

[dundarach]

Hopefully a simple question to people who know more about these things than me...

Is there a way to wire a simple speed controller in between the batteries and the motors of say 4.5v and 9v motors, could I use a volume type rotary pot or would this overheat?

Also if this is an easy one to answer, does anyone know of a simple after market RC speed controller I could drop in?

Many thanks

Chris

[Hrw-Amen]

What are you asking for? There is always the Power Functions set up with the IR Unit and remote control for speed (Which works just as well for the old 4.5V system as it does the new PF system.) or the older 9V system where the power and subsequently speed is adjusted as in a standard model railway. I assume that you know about those though?

Or are you looking for an actual controller wired between the batteries and motor that would actually be attached to the train some how?

[dundarach]

Yes I've got some power functions etc

What I'm after is an inline mod between the battery box and a 4.5v motor brick to vary the speed

So if I take one wire, cut it, insert a rotary volume switch (potentiometer?) would this work?

And moving on from a simple speed control - could I wire a simple rc into this line

So I don't want to use power functions - I want to leave the normal 4.5v motor brick and battery box - however want to control the speed

[1974]

You could wire a potentiometer inline, but it's not optimal. PWM is better and that is what PF uses. Depending on your electrical skills you could wire up an LM317 (find a datasheet, it's all there. You need a 120r resistor and a 4k7 potentiometer + some caps). This will give you a 1,25V to around 3,9V variable psu

If you just want to use a pot, then you need to find out how much power the motor draws. If it's say 100mA, a suitable pot would be (4,5V-1V)/0,1 = 35r .. get a 4W type just to be sure

[dundarach]

1974 - that made no sense, however firstly many thanks for the reply and second, never afraid to try ill go google the points and learn :-)

I was rather hoping there was a cheapo solution I could wire in, in one go, however will go experiment

Any other help would be welcomed, thanks again everyone :-)

[Duq]

You're probably looking for something like this: http://www.maplin.co.uk/motor-speed-regulation-unit-9312

[1974]

Sorry ..

Potentiometer : 30-40 Ohm 4W

Can't seem to find a UK dealer (Maplin got none, ebay.co.uk none either)

That regulator Duq linked to looks nifty. Says 6-15V but it'll most porbably work with 4,5V too. Speed regulation looks to be a pian though (trimmer under the heatsink), you might wanna change that for a potentiometer of the same value (1/4W is fine)

[dundarach]

Thanks chaps, yes the maplin one is the kind of thing, as you say with a knob rather than a screw adjustment.

What is irritating is I could buy a cheap rc car from eBay which has everything including speed controller and rc control for less than a fiver, if I could find one which worked on say 5v could I not just butcher it to fit the lego train - thus having cheap rc for my battery powered 4.5 locos....

As I don't really want to convert these to power functions and would rather not grab them as they pass to turn them off..and speed control would be nice as for shunting etc...

Will keep looking, especially as I now have some better terms to google etc.

Thanks again

For example http://www.ebay.co.uk/itm/Subaru-Impreza-Radio-Controlled-Car-/271175469740?pt=UK_ToysGames_RadioControlled_JN&hash=item3f23514aac seems to be the correct voltage with speed control and rc - now if only the guts of that we're easily removed that'd be what I was after....

[dundarach]

Right would this work, if so I'll either order one, or search for similar in the uk...

http://www.ebay.co.uk/itm/5V-30V-5A-Reversible-DC-Motor-Speed-Control-PWM-Controller-ideal-for-6V-12V-24V-/150854583486?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item231fa244be

[Duq]

For the 6V controller I would suggest contacting the seller. Sometimes those circuit boards do need a certain minimum voltage for certain components to work.

For a tenner I'd give that Subaru a go. Worst case you have a cheap toy.

[kieran]

Right would this work, if so I'll either order one, or search for similar in the uk...

http://www.ebay.co.uk/itm/5V-30V-5A-Reversible-DC-Motor-Speed-Control-PWM-Controller-ideal-for-6V-12V-24V-/150854583486?pt=UK_BOI_Industrial_Automation_Control_ET&hash=item231fa244be

You may have some issues with a good speed on this. The first issue is that the max output is 95% duty cycle and then you have to factor in the voltage drop of the output stage approx 0.7v that assumes the own controller will be happy with the input voltage of 4.5. I bet it needs 3.3v min so assuming there is a liner reg on the input stage you may just get it to work but the topmspeed will be no where near the top speed of a 4.5v batter pack connected directly. All that said for less than £15 it may be worth a go

[hoeij]

Hopefully a simple question to people who know more about these things than me...

Is there a way to wire a simple speed controller in between the batteries and the motors of say 4.5v and 9v motors, could I use a volume type rotary pot or would this overheat?

Also if this is an easy one to answer, does anyone know of a simple after market RC speed controller I could drop in?

Many thanks

Chris

I wouldn't put in any rotary pot.

Take the 9V battery box, but put in only 4 real AAA batteries (and two dummies). If you use

rechargeable batteries, the nominal voltage is now 4 * 1.2 = 4.8 volt. This is fine

for the 4.5 V motor (even 6 volts is no problem for a 4.5 V motor).

The PF receiver works fine on 6 volts (or 4.8 volts) as well.

[1974]

I just wired a 40r/5w pot inline with this one :

.. connected to a 4,5V battery. Worked fairly well

If you can't find a suitable pot in the UK, pm me and I'll send you one

Edited April 10, 2013 by 1974

[alainneke]

Yes I've got some power functions etc

What I'm after is an inline mod between the battery box and a 4.5v motor brick to vary the speed

So if I take one wire, cut it, insert a rotary volume switch (potentiometer?) would this work?

And moving on from a simple speed control - could I wire a simple rc into this line

So I don't want to use power functions - I want to leave the normal 4.5v motor brick and battery box - however want to control the speed

Like others have said, I would just wire a PF IR receiver in between the 4,5 battery holder and 4,5V motor: this doesn't require you to replace the motor and battery holder. You'll have to cut up 1 PF extension cable to get this to work: use one half to connect the motor to the receiver (connect the middle two wires to the motor), use the other half to connect the IR receiver lead to the battery holder (connect the outer two wires to the battery holder).

Good luck!

Edited April 10, 2013 by alainneke

[1974]

All fine suggestions, but the OP did write :

So I don't want to use power functions - I want to leave the normal 4.5v motor brick and battery box - however want to control the speed

[dundarach]

Thanks for all the help everyone...

The most cost effective and simplest solution is indeed to use a PF receiver....

Here was me thinking I could build something cheaper and easier, when in fact good old Lego have already done it! - right of to the Lego online shop :)