I’m planning my first HO layout in over thirty years. I will be designing my own throttles and logic for the layout. NO DCC!
Any comments about which is best for the small motors found in the typical HO loco, straight filtered Direct Current or Pulse Width Modulation (PWM)?
If PWM, what frequency?
Tim
For starters, www.modelrec.com
Both have advantages and disadvantages. Biggest problem with pulse is it hums like dcc and can overheat and burn up some dc motors, esp. old HO and n scale ones. The frequency of pulse units have always been 60 Hz(?), it’s what comes out of the wall. They used chopped half ac waveforms to control speed. Seems to me that changing the frequency would change the pitch of the hum and also maybe make a motor run hotter. It also sounds like a lot of cost and work to build a variable frequency power supply to test. Sounds like a science fair project to me.
As an electronics technician, I have always found that pure DC with feedback works better than pulsed supplies. There are some very simple feed back controller circuits around that use two transisters and a dollars worth of resistors and capacitors. The principle is that feed back compensates for load up hill, and downhill it prevents free wheeling runaway. A great test is to use a quality bench power supply and to vary the voltage from 0-12 volts to control the train. You will be amazed how nicely the train runs. What makes me laugh are the old school modellers who insist their vintage power packs using reohstats are “the best ever made”.
I have also used old AT computer power supplies and used an adjustable voltage regulator from radioshack to build an “on the cheap power pack”. It supplies constant voltage regardless of load. Works well but limits train speed to 12 volts. But really Tim, DCC rules. I think you should reconsider using it. I have used and played with all three and would never go back to switches and block systems. Spend your rescources on automating dcc if you are so inclined.
I’m planning my first HO layout in over thirty years. I will be designing my own throttles and logic for the layout. NO DCC!
Any comments about which is best for the small motors found in the typical HO loco, straight filtered Direct Current or Pulse Width Modulation (PWM)?
If PWM, what frequency?
Tim
For starters, www.modelrec.com
Both have advantages and disadvantages. Biggest problem with pulse is it hums like dcc and can overheat and burn up some dc motors, esp. old HO and n scale ones. The frequency of pulse units have always been 60 Hz(?), it’s what comes out of the wall. They used chopped half ac waveforms to control speed. Seems to me that changing the frequency would change the pitch of the hum and also maybe make a motor run hotter. It also sounds like a lot of cost and work to build a variable frequency power supply to test. Sounds like a science fair project to me.
As an electronics technician, I have always found that pure DC with feedback works better than pulsed supplies. There are some very simple feed back controller circuits around that use two transisters and a dollars worth of resistors and capacitors. The principle is that feed back compensates for load up hill, and downhill it prevents free wheeling runaway. A great test is to use a quality bench power supply and to vary the voltage from 0-12 volts to control the train. You will be amazed how nicely the train runs. What makes me laugh are the old school modellers who insist their vintage power packs using reohstats are “the best ever made”.
I have also used old AT computer power supplies and used an adjustable voltage regulator from radioshack to build an “on the cheap power pack”. It supplies constant voltage regardless of load. Works well but limits train speed to 12 volts. But really Tim, DCC rules. I think you should reconsider using it. I have used and played with all three and would never go back to switches and block systems. Spend your rescources on automating dcc if you are so inclined.