Hi,
Have a long time used Pic 4520 acting as a time and temperature controller with a NTC sensor to its Analogue port, all powered from its own 12v linear transformer.
Today we added a led driver as below to an array of 10 x 3w leds , the driver needs a control voltage of 0 -10 v DC signal ( not pwm) , so we took a tap from the Pics 12v dc power supply and use a little buck converter as the variable control.
The leds work fine, but the Pics temp sensor control goes haywire, sometimes too high, next read too low ?! ( x16 averaged readings)
The rest of the Pics functions /lcd display seem to work as normal.
Found that if we used a little mains to12v power brick to power the control voltage/buck converter instead of the Pics 12v supply, then things run ok.
To us this suggests it not as we first thought interference on the cable from the NTC , more something on the power lines ??
Any suggestions as to exactly whats causing the interference and if there is a simple way we can eliminate the problem and run the control voltage from the Pics power supply.
Have a long time used Pic 4520 acting as a time and temperature controller with a NTC sensor to its Analogue port, all powered from its own 12v linear transformer.
Today we added a led driver as below to an array of 10 x 3w leds , the driver needs a control voltage of 0 -10 v DC signal ( not pwm) , so we took a tap from the Pics 12v dc power supply and use a little buck converter as the variable control.
The leds work fine, but the Pics temp sensor control goes haywire, sometimes too high, next read too low ?! ( x16 averaged readings)
The rest of the Pics functions /lcd display seem to work as normal.
Found that if we used a little mains to12v power brick to power the control voltage/buck converter instead of the Pics 12v supply, then things run ok.
To us this suggests it not as we first thought interference on the cable from the NTC , more something on the power lines ??
Any suggestions as to exactly whats causing the interference and if there is a simple way we can eliminate the problem and run the control voltage from the Pics power supply.