<html><body><div style="color:#000; background-color:#fff; font-family:arial, helvetica, sans-serif;font-size:12pt"><div><span style="font-family: 'times new roman', 'new york', times, serif;">It's just that some of us are very curious. :-)</span><span><br></span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: arial, helvetica, sans-serif; background-color: transparent; font-style: normal;"><span style="font-family: 'times new roman', 'new york', times, serif;"><br></span></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style: normal;">+1 on curious.</div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif;
background-color: transparent; font-style: normal;">Also, on the power control discussion, one of the best circuit protection plans is to use opto-isolators. I did not see that mentioned. The basic concept is you only power an led witch turns on a photo transistor, which completely isolates your microprocessor from back EMF issues. This does not protect the other circuit from back EMF, so you still need to deal with it, but usually those components are not as sensitive. Here is the best Motor H-Bridge design I have found and it is entirely controlled through opto-isolators. </div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style: normal;"><a
href="http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html" style="background-color: transparent;">http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html</a><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style: normal;">One limitation to opto-isolators is if you need a certain frequency response. Opto-isolators have that limitation. If you need to pulse them faster than they can handle, then it will not work for you. This is a minor limitation to most of our applications.</div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style:
normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 16px; font-family: 'times new roman', 'new york', times, serif; background-color: transparent; font-style: normal;">John Vaughters</div> </div></body></html>