PWM for testing purposes - Page 1
Forum section: electronics / projects

author: Bill G
author_rank: Newbie
timestamp: December 25, 2016, 04:21:14 pm
content: Hi everyone, new here but I have been lurking for awhile. I work mainly on industrial / heavy equipment and many times find myself at a loss to confirm or reject results in troubleshooting some electro hydraulic valves. Most of these are in the 12-48 dc volt range pwm proportional valves. Very seldom do the manufacturers provide actual specifications or duty cycle nor do they provide an expected wave form. If the cost to replace was minimal a simple substitution method would probably be ok but many times the labor and material cost can be in the many hundreds or thousands of dollars.My question is this, would one of thesehttp://www.ebay.com/itm/6V-90V-15A-Pulse-Width-Modulator-PWM-DC-Motor-Speed-Control-Switch-Controller-DH-/171977923891?hash=item280aaedd33:g:czoAAOSwo6lWJufGwork for a test device to power a valve given that it falls within the parameters (volts and current) that are known? Or would it be better to build something that is better suited? I realize that more information would be helpful but I work on such a wide variety that specifics would be hard to average. The controls can be temperamental and sometimes it is easier to start backwards and make sure that the hydraulics system works properly before starting on the electrical end. Thanks for any help or any information that you deem relevant.

author: madires
author_rank: Super Contributor
timestamp: December 25, 2016, 04:47:27 pm
content: Do the electro hydraulic valves require a specific PWM frequency? That ebay PWM controller has a fixed frequency of 15kHz. Maybe you need something with a variable frequency to support different valves.

author: Bill G
author_rank: Newbie
timestamp: December 25, 2016, 04:59:56 pm
content: Thank you for the reply. i would have to say that a variable frequency would be a benefit as most mfg's don't publish the spec. I usually scope the output and try to troubleshoot from there. So many times I could match the frequency if I had that capability.

author: Seekonk
author_rank: Super Contributor
timestamp: December 25, 2016, 08:44:09 pm
content: Those little modules are handy, I just bought a couple of them. they would probably work. Do you need bidirectional? I In any testing, I like repeatability. If I was doing this I would use one of those 328 NANO boards for under $3. That would allow me to PWM it at 120 or 240Hz to give it some dither and could get fixed PWM values from a keyboard. Not that hard a program. But if you want to go simple I'd try those boards. I just got a couple of the board that have SKU-444 on the back and 3 heat sinks on the front. Haven't fired them up yet but I could probably give you some advice later if there was a problem and wanted to change frequency etc.

author: Bill G
author_rank: Newbie
timestamp: December 26, 2016, 12:36:21 am
content: Thanks Seekonk for the reply, I would prefer to keep it simple. Many times the location and situation doesn't afford much real estate for test equipment (and me) and maneuverability. It would be nice to be able to adjust the frequency as a troubleshooting tool but adding the extra hardware may in fact make it more difficult. I don't need bidirectional capabilities.

author: Simon
author_rank: Unknown
timestamp: December 26, 2016, 05:40:29 pm
content: So you need a micro with two pots and a MOSFET driver followed by a MOSFET rated to the voltage you need with a back EMF diode.Sent from my phone so mind the autocorrect.

author: Bill G
author_rank: Newbie
timestamp: December 27, 2016, 12:42:33 am
content: Thanks Simon, I'm not that familiar with the hardware (micros) to make an educated decision. Do you have any suggestions? I am looking for something that will stand up under the rigors of the type of equipment that I work on. Usually rain is not a problem although humidity and cold can be. Thank you