Using Track power to supply constant voltagegreenspun.com : LUSENET : Wiring for DCC : One Thread
I would like to use track power to power a device located in a piece of rolling stock. Is there a simple circuit that I can use to supply this power. I was thinking of using a 7812 voltage regulator for a regulated 12 volt output, but do not know how to hook it up to the trackpower. I do know how to get power from the track through the wheels into the car, but from there I am lost. I need a circuit that would not load down the DCC signals.
-- Paul Havasi (firstname.lastname@example.org), December 19, 2001
Connect up a full-wave diode bridge rated for at least 50 volts. connect the 2 AC leads to the rail pick-ups. Connect the (+) and (-) DC output through a 10 ohm 1/2W resistor to an electrolytic capacitor, 47-100 mfd, 25-35 volts. The resistor is necessary to limit inrush amps. Feed your 7812 from there. But capacitor voltage will be 12-14 volts depending on DCC booster & local load, so you may have difficulty getting a fully regulated 12Vdc. A regulated 10 Vdc should be easy. You could substitute a 16 volt zener across the cap instead of the regulator and use whatever track voltage is available, up to 16 volts. (The zener is there to clip off ocasional excess voltage spikes and protect your circuit.) If you absolutely need regulated 12 Vdc, contact me off-list & I'll send you a voltage booster circuit design.
-- Don Vollrath (email@example.com), December 19, 2001.
I would do as Don suggests except substitute a LM2941 regulator. This is a "low-overhead" device, meaning it's possible to get an output voltage only slightly less than the input. It's also programmable with a pair of resistors to get any voltage that your want. I've used track powered devices such as snow plow motors and caboose markers with battery float since 1967 powered with 20kHz riding on the the DC. Old technology of course. With DCC today, many things are possible and easy. Check the Teton Short Line website at: http://www.ida.net/users/tetonsl/railroad/ for more electronic ideas.
-- Wayne Roderick (firstname.lastname@example.org), December 19, 2001.