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I am building a controller for a snow plow and have run into one small problem with valve operation. The controller uses multiple contacts switched by one handle. In operation the switch closes two contacts, one for the motor relay and the other for a coil on a hydraulic spool valve. When the circuit is turned off, both motor and valve stop at the same time and cause hydraulic slamming.

I would like to keep the valve (coil) on for approximately 2.5ms longer to avoid the slam. Could I use a capacitor? If so, of what rating would it have to be? The circuit is 12 volts and the coil draws 1.7 amps.

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  • \$\begingroup\$ What is the purpose of the valve anyway, if they are both turned off/on at the same time? The spool should have a return path, aka bypass, when it is not engaged. In such way the motor starts up unloaded, you switch the valve on and the fluid is being pumped into the circuit. At power loss, the valve closes and unloads the hyd. pump with bypass, the motor runs down. \$\endgroup\$ – Marko Buršič Feb 13 '17 at 20:25
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the retarder effect of a capacitor is not exactly, you need a retarder circuit it, will be adjustable and you can use a 555(monostable) circuit , also you have to be aware of the limits(Amperes and potence) of the 555 you will buy, not all the chip's have equals limits i hope it will help you.

http://www.ohmslawcalculator.com/555-monostable-calculator

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