adccommunitymod (AutomationDirect) asked a question.
Created Date: May 18,2017
Created By: bsinkovich
**** This post has been imported from our legacy forum. Information in this post may be outdated and links contained in the post may no longer work.****
Using a Click digital out trying to control a speed of either a computer fan 24v or a 120v ac fan. I wrote a time base type of control to output to the digital out. The shortest time base that works with the scan time I/O of the Click is 300ms. Works well from 5%-95%. Example of the time base control, at50% the output is on 150ms-off 150ms. At 10% output is on 30ms-off 270ms. This works great for heater control. So I have a pulse output from the click connected to a SSR to power a ac fan. The on/off cycle 3ish times a second is not fast enough and the fan oscillates. I could put a capacitor on the output and get a sudo voltage output to control a drive. Any ideas on what I can do to drive a small fan(ac or dc) speed? A cheep PWM dc motor speed control with voltage control? Cheep phase angle ac SSR with voltage input? Thanks Brad
Created Date: May 18,2017
Created by: bsinkovich
Using a Click digital out trying to control a speed of either a computer fan 24v or a 120v ac fan. I wrote a time base type of control to output to the digital out. The shortest time base that works with the scan time I/O of the Click is 300ms. Works well from 5%-95%. Example of the time base control, at50% the output is on 150ms-off 150ms. At 10% output is on 30ms-off 270ms. This works great for heater control. So I have a pulse output from the click connected to a SSR to power a ac fan. The on/off cycle 3ish times a second is not fast enough and the fan oscillates. I could put a capacitor on the output and get a sudo voltage output to control a drive. Any ideas on what I can do to drive a small fan(ac or dc) speed? A cheep PWM dc motor speed control with voltage control? Cheep phase angle ac SSR with voltage input?
Thanks Brad
Created Date: May 19,2017
Created by: Adisharr
If you don't need to use a Click, a small microcontroller would be able to do this easily. Unfortunately as you know, The Click lacks a PWM instruction which causes you to be scan time based. I would think you could get a faster scan time but haven't tried anything.
Created Date: May 19,2017
Created by: BobO
BRX does PWM, but it cost a bit more than Click. Your time is definitely worth something though.
Created Date: May 19,2017
Created by: OpZed
Look into using a Software Interrupt on an Interval Time, and then inside the Interrupt Program you will have: Out, Set, Reset with a new option for Immediate output to the Y-bits. Keep the interrupt routine as short as possible.
Created Date: May 19,2017
Created by: Brandon_
There are quite a few very inexpensive 0-10v to PWM boards out there. You could add a 0-10v output analog card to the Click, then control the PWM board with that.
Created Date: May 19,2017
Created by: bsinkovich
Looks like I will use an Arduino Pro Trinket, $7. Use the digital in to time my slow Click pwm on to off and convert it to a base 25kHz pwm to run the computer fan. I think the 25kHz is the standard for the PWM computer fans and the timing of the arduino can be changed to the 25kHz pwm base. The Trinket runs at 16Mhz so I should have enough speed. It will also take a 12vdc to run which is what the fan needs anyway. This way I stay digital all the way thru and let the fan take care of the feedback and speed. Now if I can figure out if the fan pwm in is a sinking or sourcing.???
PS Thanks everyone for the replies