PSN-L Email List Message

Subject: Homemade Velocity sensor
From: Geoffrey gmvoeth@...........
Date: Sat, 12 Feb 2011 06:03:37 +0000

Hello PSN;

I saw this FLV movie by one of you
showing how to put two magnets together
on a steel plate and this is what I got,

I plan on using a setup like this with one
coil on the + side and one coil on the
- side of a differential preamp.

The black mark of each coil will go to ground.

There is about 85 turns of AWG 30 wire with a resistance
of 3.8 ohms.

With a X1000 preamp running on split supply of 3V each
I get +/-2V peak moving either coil with my hand
between the magnets.

I may rewind the coils to be exactly identical in resistance
with possibly 100 turns instead of 85 to try and offset
drift relating to temp changes putting the preamp outside.
Using two coils instead of one should double the sensor gain.

I am not able to get decent flexible cloth wire to connect the
coil in a moving way to anything so I plan on fixing the
coil to ground and the magnets affixed to the pendulum.
I know you don’t like this way but I have tried
it in the past with relatively good results.

Is this the right way to go for a home built unit ?

I have an AVI posted on my web site but unless someone really wants to see it
(42MB) file,  I will not post the link here.




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