# Zenier diode

I’m working with the circuit that’s 24 volts and up to 200 amps it needs to start at approximately 20 amps and oscillate up to 200 amps within one second and remain there until the contactor is released and then revert to its beginning state at 20 amps to begin again delay circuits don’t provide the 280 amp start and saw start as complex expensive and usually not 200 amps I need some component that provides this oscillation from partial current to full current and perhaps as zinear diode is the answer but if it is I need to know which one and I need to have the details of the circuit and other components. Please help if you can.

Welcome to the forum.

Oscillate means to switch between states, so it appears you are asking for a power supply circuit that switches back and forth between 20 amps and 200 Amps while maintaining 24V.

Ohms law says that won’t work because the resistance part of the equation is the load. The supply will have to vary the output voltage to make the the current match the load’s equivalent resistance.

It will help understand what you want, if you describe the system, it’s components and the step by step behavior you want.

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First of all thank you so much for your response.
I have built a water cooler for a TIG welder and I want to to set up a circuit that will allow me to strike an arc pull away quickly and start welding. That’s why I need the reduced amperage for about a second then back up to whatever my voltage is set at with the maximum of 200 amps. I’m trying to keep this as simple as possible hoping that it could simply be added in the load so that it restricts amperage for that one second and then goes right back to full amperage. Since I’m a beginner I have no idea how to do this. I don’t want to impose upon anyone and I realize that time is valuable. Anyway you can help me will be appreciated. Possibly this will take a step-by-step approach. Part of the problem that I have is that the circuits that I have visited would not hold 200 amps so I have to have a way to get it from its diminutive form to full amperage based on wire size etc.

That information will help a lot.

Unfortunately I have no experience in the drive electronics for TIG welding, but I’m willing to bet others on the forum will know about these circuits and will chime in later.

It is typical for TIG welding systems to provide users control over the output using a foot pedal or torch-mounted control, so I’m assuming that the overall goal here is to improvise a system to allow use of a TIG torch with a non-TIG source by providing a reduced output for a scratch-start procedure.

A zener diode is not likely to be part of that equation. A more suitable approach might be to place a large resistor such as this one in series with the leads, and short it out with a contactor of suitable size, controlled perhaps with a circuit incorporating a current sensor of some kind and an appropriate delay circuit, possibly based on use of a 555 timer (should be lots of material about that online) in one-shot mode. One could also simplify things (a lot) by controlling the contactor manually with a foot pedal or switch of some sort during the start process.

These references should be understood more as examples than recommendations, since I can only guess at what sort of resistance value might be suitable, and the characteristics of the source to be used will play a role.

Unfortunately we at DK are not prepared to offer step-by-step guidance for projects of this sort, but perhaps the idea would be enough to get you started.

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Right you are. It does provide a start and let me say that I’m aware that most people are using sometimes wrist at foot switch or torch mounted switch which I’m attempting to avoid. Some of the things you mentioned have come into my view before therefore I will attempt to move forward using your information. Thank you again for your input.