Need 100hz fixed frequency variable pwm solenoid driver

sport270

Posts17
100hz fixed frequency variable pwm solenoid driver

i have been bouncing around different solutions to a problem. I have been trying to make a variable frequency & variable duty cycle driver for 12vdc proportional solenoid. I have come to the conclusion that i only need adjustable duty cycle with a fixed 100hz frequency. The variable duty cycle is really only to set a % of flow for a proportional electrohydraulic pump control. Once i get it to the output i need, it will stay fixed, except ramping up & down to start & stop it. i have need for three of these signals to control one piece of off road equipment. And i need them to be very stable.
i was going to use some simple 555 based, but i also need serial lcd screen to show RPM of the shaft speed these pumps control. I have Quickstart propeller, Bs2, PWMPAL, DV103H, all at my disposal. Can anyone help with a absolute for sure way to do this, as i have been trying all of these and getting no where. .. Thanks for any help

sport270

Posts27

[h=2] Re: 100hz fixed frequency variable pwm[/h]

i am wondering if i cant just use an analog voltage to do this. since i am only turning this unit on to a set point and not changing it, except to ramp up & down. I shou;d only need the pwm signal if i was varying the output, so to avoid valve stiction. but since i am just going to a set point or 4.24 vdc why would it not work to just use a bs2 and output an analog voltage. mabye even have it watch the shaft signsl and vsary the voltage to keep shaft rpm within a set window. what would be the simplest bs2 code to just output 4.0 vdc and what external parts woukd i need to buffer it.

Mickster

I suspect that you are going to require some form of closed loop if you are looking for stability. Either feedback from the valve's spool (lvdt is common with prop valves) or a true closed servo loop where you would be controlling the position of the load.