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I'm buying this solenoid:

enter image description here

The data are:

  • Voltage: 12V DC
  • Current: 8A

I need to build a kicker: push a button, capacitor charge, when is charged the solenoid kick an object.

I want to do it with Arduino, and I have a 2-channel relay module 12V with optical coupler protection.

When I push a button with the first relay channel I charge the capacitor using a DC-DC boost converter 8~32V to 45~390V booster module 40W, and when the capacitor is fully charged, I will power the solenoid with the second relay channel.

I tried to read something, but I don't understand if a 4700μF 63VDC capacitor is ok for my circuit.

enter image description here

Links: Video 1, Video 2

This is basically my circuit: I want to use a cheaper capacitor and I want to use a typical DC power source instead of the battery.

JYelton
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Roberto Pezzali
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    Show us your circuit. There's a schematic editor built in to the question editor if you hit the edit button. – Hearth Feb 12 '19 at 16:26
  • @JYelton is the document I read, but I don't understand it. – Roberto Pezzali Feb 12 '19 at 16:29
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    Your circuit specifies a voltage and you want to use something that's barely a tenth that voltage rating? Your capacitor will literally explode. – Hearth Feb 12 '19 at 16:43
  • What @Hearth said. Also your switching relay will eventually start to fail as the current spike from discharging that cap with 360+ Volts will exceed the instantaneous current rating and result in premature failure. – KalleMP Feb 14 '19 at 20:26

1 Answers1

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The solenoid you linked is a 12V device that draws 8A.

The "kicker" devices shown in the videos are using a boost converter to achieve up to 390 volts, which is applied to the capacitor to charge it.

Video frame where 390 volts is measured

(Video frame shows 390 volts being measured at boost converter output)

The snap action switch then connects the capacitor to the solenoid, which effectively overdrives the solenoid to produce the strong "kick" that is demonstrated.

First, an extremely important point. You should NOT be working with high voltages unless you know what you are doing. High voltage capacitors can be lethal. You have been warned.

If you are converting the input voltage to anything that exceeds the capacitor's rating (63V), it will fail and likely explode. Generally you should select a capacitor with a voltage rating that exceeds the intended voltage by a safety margin (10% or more). If you are going to use 390V as shown in the video, then you absolutely must use a capacitor that is rated at least that high. The one used in the video is rated for 450V.

Short answer: NO. The capacitor you're asking about will NOT work.

Going a bit further, assuming you have a properly rated capacitor...

In a purely DC scenario, a 12V 8A inductor (solenoid) will have a coil resistance of about 1.5Ω. Applying 390V will draw about 260A, if only for a short time. Obviously the duty cycle of this device is very short -- and necessarily so -- operating a 12V solenoid with 390V for any longer duration would cause it to fail very quickly. Even so, I would not expect such a solenoid to perform well for very long with such abuse.

JYelton
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  • now is very clear. Do you suggect to use a lithium battery? Of course I can adjuct the output voltage of the 45~390V Booster Module so I can limit it to 55 volt, that is ok for a lower voltage capacitor. This can be also healty for the solenoid. – Roberto Pezzali Feb 12 '19 at 17:06
  • If one goal is to save money, you might be able to find a less expensive boost converter which has a lower voltage output (such as 50-60V, instead of 45-390). The battery chemistry is not important (in this case) for the operation of the circuit, but factors in when you consider how many times you can operate the device before recharging, cost, weight, etc. – JYelton Feb 12 '19 at 17:14
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    the booster output is +45~390V continuously adjustable (but the default output is ±50V) so i can keep it to the default and use a 63 V capacitor. I will use a 220V power adapter, I have some of them! Thank you for your help, your explanation is very clear! – Roberto Pezzali Feb 12 '19 at 17:20
  • Please be careful! Even at 48+ volts bad things can happen! Good luck with your project. – JYelton Feb 12 '19 at 17:31
  • Even at 50V you will be exceeding the relay contact current rating. It will eventually fail though not as fast as if you operated at 390V. Note also that the force of the solenoid will be a LOT less with 50V than 390V. Also note that the relay contacts are rated at only 30V with a DC resistive load and 24V DC for a inductive load (coil) so you are exceeding that rating by a lot as well. Contacts may burn off or weld shut sooner than wished for. – KalleMP Feb 14 '19 at 20:31