# Constructing a 1Hz 50 Hz 500 Hz 5Khz 30 Khz 50 khz Switching Device

1. Jan 14, 2013

### gedfire

Hello All,

I am thinking about pulsing the power from individual 9-12 volt Batteries @ the different frequencies of 1 Hz, 50 hz, 500hz 5 khz 30 khz and 50khz .

All I want to do is to create a pulse DC charge from a 9 volt or 12 volt battery.Car or Motor Cycle batteries are my targets.

I want to pulse this DC voltage using as little amperage as possible to a capacitor.Now I would also want to know what kind of protective device I could use to prevent the Super Capacitor (50F at 12 volts ) from over charging? Zener Diode, varistor,gas discharge tube etc? Please let me know the best components to use and if possible, the specifications based on the parameters I have outlined.

Can MOSFETS be used? If so how? The simplified version if possible please

Best regards,

Gary

2. Jan 14, 2013

### vk6kro

If you produce pulses that vary from 0 volts to 12 volts, then you can't overcharge your 12 V rated capacitor. Make it 10 volts to be safe.

You can generate a range of frequencies in many ways, but an easy way is to use a 555 chip. You can find a circuit that uses only one resistor and one capacitor if you use Google in image mode.

A MOSFET can be used to switch the current to the capacitor, but the voltage across the capacitor will not look like a pulse. It will be like a charging capacitor where the voltage is rising to the peak value of the input pulse.

You can limit the current by placing a suitable resistor in series with the capacitor.

Perhaps you could explain what you are trying to do?

3. Jan 14, 2013

### Staff: Mentor

You other similar thread and this one are very confused and confusing. Could you please say exactly what you are trying to do?

4. Jan 18, 2013

### gedfire

Hi,

Thank you for replying.You say I cannot overcharge a capacitor as long as I pulse it with a suitable voltage.I am pulsing it with a dc voltage through a diode.I thought the charge would accumulate until it passes the voltage rating and possibly explode?

I am trying to pulse charge a capacitor though a diode placed on one leg.

If you need anymore details please let me know.

Ged

5. Jan 18, 2013

### gedfire

I am trying to charge a capacitor through using a diode on one leg.Like this:

but with a solid state version like this:

In this video the capacitor voltage increased....what if the gentleman had allowed the charging to continue?

Hope this answers your questions.After charging the capacitor,I want to use it to power a load safely.

Thanks

Ged

Last edited by a moderator: Sep 25, 2014
6. Jan 18, 2013

### vk6kro

No, that can't happen.

The diode will only conduct if the voltage on its anode is more positive (by at least 0.7 volts) than the voltage on the cathode.

So, if the capacitor is already charged to, say, 11.3 volts, the voltage on the anode has to be at least 12 volts before the diode will conduct.

If the peak input pulse value is 12 volts, then charging will stop.