Yes it has, during the run up to Christmas things get a bit crazy in the Hobley household. That’s not to say I’ve not been very busy on the CNC router, but mainly producing presents and other festive stuff.
I have been working on a tip-top secret project featuring the Ebow-clone I put together in the last post – but this is quite a way off just yet.
I was invited by my buddies at Make to put together a Christmas gift guide, and so rather than go for glitz and glamo[u]r I decided to go for the 10 most practical Maker tools I’ve used in 2011…
I’ve been meaning to build one of these for ages.
Can anyone guess what it is?
It’s not a Taser, or one of those shocking buzzer things – the clue is that the coils are well “potted” and have very different gauges of wire.
Answers on a postcard please, or in the comments…
UPDATE : Correctly identified as a “guitar sustainerizer” otherwise known as an Ebow.
The circuit is a simple audio amplifier based on the LM386 (or in my case the NTE823) IC.
The two coils are taken from old telephone pickups – one (input) has a small rare earth magnet on the back, the other (output) was unwound and rewound with about 300 turns of #32 wire – this coil now has a resistance of just under 8 ohms. I tried a 4 ohm output coil, but the IC got too hot so I doubled the turns.
Note – I recently found a better candidate to make the coils with – tiny PC speakers.
The input coil has a resistance of 250 ohms – this is probably too high – I read somewhere that 50 ohms is probably better – so I may remove some of the turns on the coil.
Tomorrow I’ll publish the circuit and the etch mask, along with a video of the device in action.
…and here’s the patent 
UPDATE2 : Here’s the schematic, placement and etch mask – click to enlarge
Steve Hobley works for a software company, but in his spare time likes to deconstruct all the lovely consumer goods with a goal to make unique and interesting things.
