I would like to provide 2 data point for DIY spot welder. One bad, another, ok. The reason for this post is just to talk about my experience, not to encourage DIY spot welder. If I wasn't on the tightest budget, I would buy from maletrics, because his/her implementation using power MOSFET is ideal to me. The price on his/her kit is also great. Highly recommend.
Note that the car battery can explode and spill sulfuric acid. So do it in a safe place; Have an emergency plan; Wear proper protection gear. Also bear in mind that all the success story you read online does not mean it is a robust solution that can be repeat over and over.
My setup:
I only paid about $10 for solenoid and battery terminal. The rest are obtained around the house.
The basic concept is to used Arduino to send a short pulse to trigger 5V relay which in turn trigger the solenoid.
There are youtube video demonstrates this concept just without the pulse time control. The solenoid coil is powered from car battery. The electrodes are soldered onto the wire. I'm using 0.2mm pure nickel strip.
My first attempt failed spectacularly. I set a pulse of 20ms and the solenoid failed(stuck) from high current which melted the nickel strip. The melted nickel strip continue to bridge the positive and negative electrode and this goes on for about 5 second until the 12awg solid copper wire de-soldered from the 10awg wire. The car battery survived and only slightly warm to touch.
My second attempt is successful. Here is what I did:
Since it is working ok, I'm desperately need a fuse to replace the magnet. Also need a foot pedal switch so I can better control the pressure on the electrodes.
Any comments or critics are welcome. Thank you.
Note that the car battery can explode and spill sulfuric acid. So do it in a safe place; Have an emergency plan; Wear proper protection gear. Also bear in mind that all the success story you read online does not mean it is a robust solution that can be repeat over and over.
My setup:
- 12V car battery with 560CCA (from my sedan)
- 10 awg silicon wire (from old APC UPS)
- 12 awg solid copper wire as electrode (ROMEX building wire)
- some random solenoid from ebay
- Car battery terminal from Advance Auto
- Arduino
- 5V relay module like this
- copper pipe smashed and drilled to use as conductor
- some neodymium magnets
- a resistor and a momentary switch button
- heat shrink tubs
I only paid about $10 for solenoid and battery terminal. The rest are obtained around the house.
The basic concept is to used Arduino to send a short pulse to trigger 5V relay which in turn trigger the solenoid.
There are youtube video demonstrates this concept just without the pulse time control. The solenoid coil is powered from car battery. The electrodes are soldered onto the wire. I'm using 0.2mm pure nickel strip.
My first attempt failed spectacularly. I set a pulse of 20ms and the solenoid failed(stuck) from high current which melted the nickel strip. The melted nickel strip continue to bridge the positive and negative electrode and this goes on for about 5 second until the 12awg solid copper wire de-soldered from the 10awg wire. The car battery survived and only slightly warm to touch.
My second attempt is successful. Here is what I did:
- fixed the solenoid by opening it up and the two pads separated by themselves.
- unscrewed the negative wire from battery and only use neodymium magnet to hold the wire onto battery terminal, so I can break the circuit quickly.
- use 12V to power the 5V relay coil instead of Arduino (control signal is still from 5V Arduino). If you don't understand, google Opto-Isolated relay module. Doing this allowed me to switch the relay faster.
- sanded the electrode tip to flat (I think this maybe the most important change)
- Change the pulse time to 15ms (I started from 2ms as minimum achievable . 10-15ms gives good weld)
Since it is working ok, I'm desperately need a fuse to replace the magnet. Also need a foot pedal switch so I can better control the pressure on the electrodes.
Any comments or critics are welcome. Thank you.
