PULSE WITH

[John J.]

Hey Guys
I am using some of your ideas for my Garden Scale Rail Road to automate it. Up comes the subject Pulse With. Pulse with is great for running train locomotives real slow.
Do you build all your own pulse with circuits or is there a read made package I can buy. I have already ordered some Stamps and PIC's to play with. To control my swithcing and stuff. Maybe later even speed.
Thanks
John J.

[greg123]

You can build you own pulse WIDTH modulation circuits (note thats its width not with, as you alter the width of the pulse, eg. it's duty cycle). The pulse width modulation (PWM) is used to control the location of a servo motor, as the longer the on time of the pulse (in milisec) the further the servo will turn.<p> For one servo, you can use a 555 timer and a variable resistor to vary the duty cylce. This can be a bit messy if your turning the pot by hand. Midi can also be used (check this months NUTS AND VOLTS for an article on MIDI control with servo's). There are also a good many chips that can do this for you...including the BASIC stamp and such. <p>Hope this helps.

[Chris Smith]

PWM is not JUST for servos, they are commonl;y used in all DC brush motors, as well as other motors.

[John J.]

Hey Guys
Thanks for the help. I just ordered a BASIC stamp kit. I have not worked with them yet so I got some learning to do. This should be fun.
thanks
John J

[John J.]

Hey Guys
Thanks for the help. I just ordered a BASIC stamp kit. I have not worked with them yet so I got some learning to do. This should be fun.
thanks
John J

[John J.]

Hey Guys
Thanks for the help. I just ordered a BASIC stamp kit. I have not worked with them yet so I got some learning to do. This should be fun.
thanks
John J

[greg123]

Your Welcome<p>Your Welcome<p>Your Welcome

[Droidwerkz]

PWM is not JUST for servos, they are commonl;y used in all DC brush motors, as well as other motors.

correct , the term servo typically applies to a motor with a built in encoder of some sort , basically if you have assembled a motor with soem type of shaft encoder attached, you have built a servo, also if you want to get really specific about it, pulse width dc motor controllers and pulse frequency dc motor are different also , pulse width modulation modifies the duty cycle (0-100%) and pulse duration (measured in fractions of a second ) whereas with a pulse frequency DC drive modifies the rate that circuit turns on/off at without varying the duty cycle (it stays at 50%) pulse duration will then be measured as (.5)X X being the frequency (hz, khz, mhz) that this controller is switching at.

try using a 741 op-amp some time as a voltage comparator and a potentiometer as a shaft encoder, when the resistance of the potentiometer equals the resistance of the comparators reference resistor you can use the output of the comparator to control a relay or h-bridge, telling the motor when to stop or reverse, likewise if you use a dual comparator you can have the motor move to a fixed position reverse, move back to its start point and reverse again infinitely like a bouncing paddle ball toy.

I';d like to talk more about ac motor control too. i just LOVE making things move!