EDM

Hello

In the MEW 117 July 2006 is an artikel on "A simple spark erosion Machine", in the circuit for the Oscillator is a switch S1 with R1-R2 and another Switch with R5-R6and R7

Are these switches two separate switches or a single xpole, and would it be posible to replace them with Potentiometors.

My knowledge of electonics is veryy limited.

Thank you for your answers

Ray

Ray,

It looks like 2 separate switches as they provide different functions.

I would not replace them with a pot, but if you did you would need to insert a resistor in series with it to provide a minimum resistance.(equal to the lowest value of the current ones)

Dave

Thank you Dave I'l keep that in mind.

I wasnt sure if it was 1 or 2 swithes, i hadnt grasped the 2 different functions.

Ray

This technology has always been of interest to me. Is there a design out there that are better than the others. Recommended reading? Cheers, Andrew

Hi Andrew,
There are few designs by Ben Fleming that look like they are more advanced that the type on Mike Cox's web page. This the the web page where he is selling his books with the design in them and the printed circuit boards for the electronics. He also has this Yahoo forum dealing with his designs.

Les.

Andrew

try the web site www.mikesworkshop.weebly.com, you will find a spar eroder under Miscellaneous.

This is where i started, the site is from Mike Cox

Good Luck

Ray

Many thanks. Les and Ray.

Hi Ray,
The intention of S2 is to change the rate of pulses. (As a very rough estimate I would say about 2 Hz) I see no reason why a potentiometer should not be used but as Dave (Steambuff) says it will need a series resistor to limit the lowest value.I would not suggest going below about 100K The values of this resistor and the value of the pot will depend on the frequency you are trying to achieve. (See the data sheet for the LM555 or LM556 to work out the values required to give the frequency range you want.) I believe that the intention of S3 is to change the pulse length but I also believe there is an error in the circuit. I believe that pin 1 and pin 2 of the LM556 should be connected together. The same comments apply to this switch and two resisters as they do to S2 in regard to replacing them with a pot. Bear in mind that if the pulse period is set longer than the period of the pulse rate the circuit will behave strangely.

Les.