IP Engineering use a simple pot controller, and I never managed to make 'em work, usually for the questions you just askedNot a fan of this idea..
There is a reason tram resistor packs are on the roof, and no-one has asked what voltage battery, and what the motor current is going to be?
'Rheostats' tend to be large, and wire-wound, for a reason.
By the time you have sourced, and paid, for a wire-wound, decent wattage potentiometer, you could get a Chinese speed controller for less.
Using a potentiometer as a rheostat for simple motor control.
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The add wire, if the wiper ever loses contact with the resistive strip inside the potentiometer, this connection ensures the circuit does not completely open, that there will still be a resistive path to the motor. Old potentiometers tend to suffer from intermittent losses of contact between the wiper and the resistive strip, and if a circuit cannot tolerate the complete loss of continuity (infinite resistance) created by this condition, that “extra” wire provides a measure of protection by maintaining circuit continuity.
Should add this an extremely inefficient method of motor control, surplus voltage is wasted as heat.
If you could elucidate further, an off the shelf, ready made unit, may serve your purpose better.............
This is an improvement, minimum electronics required!
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Off the shelf solutions....
Add DPDT switch for reversingFind great deals for Mini DC Motor PWM Speed Controller 3V 6V 12V 24V 35VDC 90W 5a DC Motor Y9R4. Shop with confidence on eBay!www.ebay.co.uk
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The following two, used on many numerous occasions, just need to add a DPDT switch for reversing.
The second one listed is in daily use as part of the control system on the two analogue display layouts, running 24/7 365 days a year.
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Then there is this mega jobbie....
PWM frequency: 16kHz. The overload and short circuit protecting current is 15A. Can adjust the speed by the external 0-5V signal. Duty Cycle adjustable: 0-100%. The maximum output power: 1000W. The maximum continuous output current :10A.www.ebay.co.uk
Several of these have been built, including the option for Linear Control, out for testing with G Scalers around the South West, can be found via this thread post #1218.
Possible (subject to feedback) could be the control system of choice for the Analogue Layout at the Exeter Garden Rail Show in October this year.
Electronic trickery, Bluetooth and WiFi versions are also out and about for testing.........................
I have one of those little speed controllers from china, and it works great. The shaft is disguised as the smoke stack/chimney. The central 'radiator' (?) is sitting on a DPDT slide switch for direction changes.I thought of placing it on the roof and building a shroud to cover it,