Hey!
Student in EE here. We are building a Thompson jumping ring circuit and have a problem with the power supply constantly hitting overcurrent and overvoltagen protection. More often voltage than current protection. Please see schematc. We are trying to run it att 20V 2A which is the project maximum alowed power. The coil has 600 turns of 0,5 mm copper wire. The arduino only acts as a on/off signal provider for the mosfet. Does anyone have a clue of what might cause the issue were having? The goal is to get a varying current in the coil.
Thanks!!!

 

Hello,

Did you measure the current?
Also the Vin of an arduino nano should be between 7 and 12 Volts.

Bertus

 

First, have you measured the actual resistance of that coil? That will allow you to calculate the steady-state current and see what the actual load is.
Next, I am guessing that you have a decent quality lab power supply with adjustable limits. So have you verified which limit it is tripping on? Voltage or current?? That matters a bit.
How are you measuring the voltage and the current???
So I have two suggestions: First, with the arduino pulsing the mosfet switch, while monitoring the supply voltage, start at a much lower voltage and observe the operation. Then gradually increase the voltage and observe the operation. At some point it will possibly start tripping the limits, probably. Compare that voltage and calculated current with what you calculated based on the measured resistance.

 

First, have you measured the actual resistance of that coil? That will allow you to calculate the steady-state current and see what the actual load is.
Next, I am guessing that you have a decent quality lab power supply with adjustable limits. So have you verified which limit it is tripping on? Voltage or current?? That matters a bit.
How are you measuring the voltage and the current???
So I have two suggestions: First, with the arduino pulsing the mosfet switch, while monitoring the supply voltage, start at a much lower voltage and observe the operation. Then gradually increase the voltage and observe the operation. At some point it will possibly start tripping the limits, probably. Compare that voltage and calculated current with what you calculated based on the measured resistance.

Yes, resistance of the coil is something like 100 ohm which we think sounds very high.
The power supply is quality. It trips at all voltages, which makes us think it has something to do with transients going back into the PS? It seems like it tries to pull a higher voltage than our set limit. But this also happens if we increase the limit to for example 30V.
We are measuring it with an oscilloscope, and the signal also looks like it has transients.
Thanks for your help!

 

Hello,

Did you measure the current?
Also the Vin of an arduino nano should be between 7 and 12 Volts.

Bertus

The PS pulls like 2A but then trips like once every second. We have only meassured the voltage in the coil and it looks like it has transients.
Ok, thanks!

 

hi jz,
The 5V supply should go to the +5V pin of the Nano not the Vin pin.
You will get transients when switching an inductive load.
What is the current output rating of the power supply?
E

 

hi jz,
The 5V supply should go to the +5V pin of the Nano not the Vin pin.
You will get transients when switching an inductive load.
What is the current output rating of the power supply?
E

Ok, thanks!
Its a RND 320-ka3005d so it looks like it's 5A?
We have set the limit to 2A though. Also have tried increasing it to like 3A but no difference.

 

Well, voltage and current work inversely hand-in-hand normally unless manipulated otherwise. In DC, the primary means of controlling or limiting current is via resistors, or amplifiers. In AC, you rely more on Inductance & Reactance. I don't see any resistors in your circuit (although I've only glanced at it). Circuit design is all about controlling how much current flows through your circuit at a specific voltage so at the end of the day the exact amount of energy necessary is consumed- no more, no less. If you consume too much or not enough, you will see voltage and current misbehave.

 

Use two separate wires to connect the controller supply IN- and OUT- and the MOS FET directly to the supply negative terminal. This will stop voltages voltage dropped on the FET ground wiring from affecting the controller ground voltage.

 

The solution is to set aside that lab power supply and get an "ELPAK" non-regulated 24 volt DC supply. Add a series fuse to it to protect it from overcurrent issues.

 

The solution is to set aside that lab power supply and get an "ELPAK" non-regulated 24 volt DC supply. Add a series fuse to it to protect it from overcurrent issues.

....and a bag full of spare fuses?

 

The "ELPAK" power supplies that I am familiar with are able to easily survive momentary overloads with no problems at all. They don't even notice those short transients in the load current. I am not even certain that the outputs would be fused.