testing a material using a circuit

Hi my name is steven and i was wondering if anyone could help me by suggesting a circuit to help me in a design and technology A-Level.I need to design a circuit to test materials and the circuit must include a 24v DC motor.The motor will move an abrasive block which will test the material and the circuit should be able to control the speed of the block and count the number of strokes the block has made and some way of changing the direction of the motor would be helpful. If anyone can help please do.
Thanks Steven.

Posted by stevent on 21/05/2003, at 20:21 GMT

You need a counter!

Hi Steven,

You could build a counting circuit using individual counter ICs such as the 4520 (see the article in issue 7 of the old Electronics in Meccano site, www.temp.eleinmec.com) but an easier solution would be to use a ready made counter module from Maplin (code FS13P, page 645 of current catalogue).

This is five digit counter so should count high enough for your application. The count input is simply a push switch, which could be arranged to be actuated by the abrasive block as it moves to and fro.

Or, if you want a non contact solution, use an opto sensor (see www.eleinmec.com/article.asp?7) or a reed switch and magnet (see www.eleinmec.com/article.asp?23)

Using a counter like this also means you don't need to control the motor using a circuit - just connect it (using a reversing switch, see www.eleinmec.com/article.asp?12) to a 24V supply.

To control the speed of the block, vary the voltage of the power supply, or if this is not possible, using the Darlington pair circit (www.eleinmec.com/article.asp?13).

Hope this helps! Reply if you need any more info.

Posted by Tim Surtell on 21/05/2003, at 21:25 GMT

Hi, Steven

Please explain in more detail, what are you trying to test
If you want any electronic counters or components for your A level projects then send me e-mail I might be able to sort out components, as I work for one of the biggest testing laboratory and when the testing ends on our projects we scrap the unused components in the skip.

Best Regards
Harry Vadgama

Posted by Harry Vadgama (h.vadgama@ntlworld.com) on 02/06/2003, at 21:57 GMT