Hello,
I'm building a replacement heater unit for my car, I'm controlling the bypass valve (controlling the amount of heat going through the radiator vs. bypassing the radiator) electronically with a PWM unit.
I originally hoped to use an off the shelf PWM controller from eBay, based on this: http://www.solorb.com/elect/pwm/pwm2/pwm3.jpg but with added voltage regulator.
It's my understanding that the frequency of the output is controlled by the 100 K resistor between pins 1 and 13, and the 10 nF capacitor between 13 and 14.
The catch here, is i'm targeting a frequency of 0.5 Hz (ish), which will involve replacing the resistor with a 500 K unit and capacitor with 1 uF, however this doesn't seem to change the frequency of the output.
Is my thinking correct here? Any suggestions, am I simply trying to get the unit to work outside of what it's designed for? If so can anyone recommend a different approach to generate a low frequency variable duty PWM output.
Thanks, Tom
I'm building a replacement heater unit for my car, I'm controlling the bypass valve (controlling the amount of heat going through the radiator vs. bypassing the radiator) electronically with a PWM unit.
I originally hoped to use an off the shelf PWM controller from eBay, based on this: http://www.solorb.com/elect/pwm/pwm2/pwm3.jpg but with added voltage regulator.
It's my understanding that the frequency of the output is controlled by the 100 K resistor between pins 1 and 13, and the 10 nF capacitor between 13 and 14.
The catch here, is i'm targeting a frequency of 0.5 Hz (ish), which will involve replacing the resistor with a 500 K unit and capacitor with 1 uF, however this doesn't seem to change the frequency of the output.
Is my thinking correct here? Any suggestions, am I simply trying to get the unit to work outside of what it's designed for? If so can anyone recommend a different approach to generate a low frequency variable duty PWM output.
Thanks, Tom