Wednesday, November 4, 2015


Ages ago I ordered an electro magnet that runs off 9v DC. It worked well. So we'll, in fact, that I ordered a second as soon as I'd texted it for strength. The plan was to operate both in opposition so that the magnets would repel each other.

Coming from China, the prices were cheap but the delivery painfully slow. The process was started on October 11th with the first magnet. The second, I ordered shortly after the first arrived.

Then the painfully slow process of waiting for it to arrive started. Today it finally arrived and it looks exactly the same. It even has the same M4 threaded hole!

With standard electro magnets, the wire is coiled around a magnetic core which is North at one end and South at the other. Reversing the polarity of the current changes the polarity of the magnet.

I put the two magnets together and put current through to find both magnets, predictably attracted each other. Reversing the current, both magnets still attracted each other. That being somewhat weird demanded more attention!

Returning to the bus, I found I'd left my lantern in the house. Fortunately I had a standard lamp in the bus and the electricity works. The lamp was located with the aid of the flashlight built into my phone then activated.

Sitting on the bus I put everything onto a breadboard. That allowed me to concentrate on aligning the magnets correctly. Everything worked as it should, attracting and repelling appropriately. Neither of the forces seemed that strong so I located my multimeter. A few moments more of hunting located the leads. Testing the meter proved the battery to be flatter than the average pancake!

It being a bit dim to locate my mini screwdriver, I ignored the flat battery in the meter and tried measuring the battery voltage. The needle swung a bit and stopped. Then I realised how old the battery in the meter was and how old the battery I was trying to use with the magnets was. They were both purchased in 2010 so clearly they have a perfect right to be dead by 2015!

Having discovered I now need fresh batteries, I paused to check my grit blaster which seems to be quite sticky. Looking at it carefully through a loupe, it was possible to see that it was indeed held together with Allen bolts. That makes life easier. I can enlarge the holes as others recommend, clean it up and try it again.

Obviously, tomorrow I need to stop off at Dollar General for some fresh batteries!

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