Microwave spot welder

[59apachegail]

I came across a free old microwave. I have been "dying" to try building a spot welder out of one. I took the transformer, power cord, door switch, handle, an old 110 light switch and a set of old car battery cables. This is not my idea I saw it on YouTube and I am a little of an electrical novice. So far this was all free stuff I had laying around just like the video. I cut and removed the secondary coil and left the spacers and primary coil. I then wrapped the old car battery cables twice over the primary coil and adapted the power cable to the primary coil. At this point I had a working spot welder crazy as it may sound.

I am planning on refining it with a proper box and lead setup, $15 worth of hardware store materials.

At the end it is low voltage but high amps. Now my question is what type of circuit breaker do I add to this setup so I don't kill myself or start a fire?

Any input is appreciated!

 

[dogdog]

one of those temperature re-settable fuse to break the primary circuit.... and size the electrical fuse according to the KVA of the transformer ? or the microwave watt that you took it out of ?

you can steal the schematic from this HF stick welder... page 15/16


https://manuals.harborfreight.com/manuals/62000-62999/62745.pdf

 

[59apachegail]

Thanks Dogdog!

How do I find that out after the fact? I got my parts last week and finally got around to start the project this week. The microwave went to the garbage already. I am armed with a VOM but still learning how to use it.

 

[dogdog]

I dunno for sure 100 percent on transformers KVAs.... but if I were to search the model number on your transformer markings...MWM0701TSS

This comes up and says 700 WATT...

https://haier.encompass.com/model/HAIMWM0701TSS/_/_/Haier/MWM0701TSS/Mwm0701tss:0.7_C_Ft._700_Watt


once you decided on that... I think you can then search for a thermal fuse (usually it's rating by temp, and amp) and stick it to the transformer core .... insulating it of cause... to prevent it from over heating...

I have a 900WATT one sitting in the back burner.... but that is what I would do... a thermal fuse , and a electrical fuse on the primary.

or try to google that transformer : MD-601AMR-1 see if you have any information what microwave it fits in.... and watt it uses....or KVA on the spec sheets.


or try to measure and guesstimate the wire size of the primary winding ?

 

[59apachegail]

Thanks Dogdog!

Much appreciated, I'll order up some goodies and get back soon.