I have a 30+ year old Model Power dc controller and the throttle jumps from 0vdc to 16vdc with no in between voltage. I tried hooking it up to a PWM to control motor speeds using my controller as a dc transformer only. The output on the transformer is 16vdc, but as soon as I hook it up to the power inputs on the PWM, the transformer output jumps to 24vdc. I realize it can be difficult to read the PWM motor lead output without an oscilloscope, but I'm wondering why the voltage jumps up to 24vdc on the transformer. The PWM has no other source of power and should act only as a "volume" control, and the output (motor terminals) should never exceed the power input voltage. Am I missing something?
PWM issue
- Thread starter Toolbelt
- Start date
Iron Horseman
Well-Known Member
First the Model Power controller is not going to be a regulated supply. Its open voltage is going to be much higher than it will be with a load. So I don't know how it would interpret the "load" of a PWM. What does it show when there is a motor on the output of the PWM?
I do know that certain combinations of capacitors and diodes called "step up" circuits can raise the voltage. Considering the normal use of a PWM it makes sense there is something inside that sets the output voltage to the max desired, despite the input. Maybe that has something to do with it.
I do know that certain combinations of capacitors and diodes called "step up" circuits can raise the voltage. Considering the normal use of a PWM it makes sense there is something inside that sets the output voltage to the max desired, despite the input. Maybe that has something to do with it.
The only "load" the transformer had was connecting it to the PWM. Because the voltage was 24vdc, I didn't want to risk testing it with my dc loco. The PWM I'm trying is supposed to act like a valve or dimmer, controlling the incoming voltage from 0-100% to its output. It's not supposed to step it up nor should it be a load to the transformer. I'm not sure what else I can hook up to the transformer to serve as a cheap voltage controller for it, that also has a reversing function? I'm just trying to get my dad's old setup working before diving into the hobby fulltime and switching over to DCC. His set was from the mid-80's.
