Total newb here, but I ve been lurking for a while.
I need to control the cycle speed of a double acting cylinder. I also need to automate the system. I've read similar threads but haven't found a clear solution.
So I'll be using a five port solenoid valve and two flow control valves on the exhaust lines to control the speed of the stroke. I also need to control the cycle speed between 10-20 cpm.
Some suggest an LM555 timer with adjustable resistor but I am thinking repeat cycle relays would work better. Question is do I need two of them for upstroke and downstroke? Any other suggestions? Thanks

 

I am assuming the cpm rate you need to automate is based on some sort of feedback data you are receiving from somewhere else in the process. Perhaps you can elaborate.

I am thinking possibly a PIC solution where you can input that data and vary your output accordingly.

 

Hydraulic or pnuematic? two or three position valve? rated voltage? Are you manually controlling speed via your meter out?

 

If the cylinders' rod is double-ended, you could use a single regulator valve on the pressure side to control the piston speed.

If the cylinders' rod is single-ended, you might still use a single regulator valve on the pressure side, but it'll have to move a fair bit when the piston changes directions. A PWM-controlled valve might be OK with that.

You could use a linear pot to track the cylinder speed and location. You might also be able to use a rotational encoder.

 

Quick word of caution. All control valves (spools) should be fully opened or fully closed when operating. Failure to do so will cause erosion at the face of the spool in the O-ring seat area., Speed should be controlled by an independant flow control and the spool then becomes a basic on off type of device. The type of system (open center/closed center) will also make a difference in the control scheme you use. A PIC or PLC can be used with great results in this type of equipment.
Bob

 

More details, it is a pneumatic system and the cylinder will be actuating a lever attached with a clevis pin. The base of the cylinder is also mounted with a clevis pin. Up stroke and down stroke speeds can be equal, the only thing I need to control are the cpm, around 20, based on the task. Power is negligeable, I only need about 25-35lbs. If it is a lot easier I can go with a fixed cycle speed of 20 cpm right from the begining.
I was thinking a 5 port 4 way 2 position valve would do.
The system needs to be automated. I was thinking repeat cycle relays but I don't know if they can be set to stay on for as long as I need within my time frames.
I am not great with circuit boards(History major...) so if you suggest a PIC, I hope its an easy build. Thanks.

 

http://www.ia.omron.com/product/family/193/index_fea.html

 

Thank you GetDeviceInfo. I read the instructions but I don't know if it's a repeat cycle timer.