Roland Andrag wrote: > > On the same sort of topic, has anyone seen a book or web page devoted to > making a circuit design bulletproof? I would love to hear a few tips from > anyone willing to share! > > Cheers > Roland No books about it AFIK, but some tips perhaps, here goes "Wagner's 10 golden rules": 1) Project it simple, less components is better, show your project around, somebody could have a better idea, but never believe on them, test it two thousand times. Remember, there is at least 10 thousand ways to drain a battery. 2) Super estimate situations, FanIn and FanOuts, always think about the weight of an 747 airplane just to transport 250 persons ... or the weight of a car to transport 4 people... never project things to works inside 10% of tolerance, it is suicide. 3) Never buy "cheap" and "under promotion" components, they may have a "nice" reason to getting rid of them. Always buy well known brand components... and *stress test* them before assembly. A 16V capacitor is not suitable to work in 12V circuits if you really want to avoid problems. Try 25 or bigger isolation voltage ones. If money can buy, use military spec components, automotive or industrial temperature packaging even if it is to work in a controlled environment. Make simple and easy tests, as heat transistors in boiling water to test their Beta gain, then put them into the freezer and repeat the test. You will be surprise how many fail. 4) Guessing is the devil's art or laziness. You have a calculator and electronic formulas, so use them wisely, and make your electronic teacher proud. 5) If a powered and working printed circuit board should stand 5 drops from 3ft high into concrete and still running without any problems, and if it is the recommended tests, make it happens 10 times from 15 ft minimum. 6) Never, never, never solder a power temperature component with straight leads to the PCB if it is also somehow screwed to a heavy heat sink screwed to the board. Temperature expand things and can brake leads, soldering, tracks. Always bend in a zig-zag (if possible) those leads to give them slack for thermal movement. A simple spring clip and silicon grease works much better than a 200lb torque bolt for thermal transfer. If your power transistor requires to conduct 3 Amps, go for a 15 amps unit. How do you like to work in that nice and warm ocean breeze at a summer sunset? this is how the transistor will works, think about it. 7) All heavy components need additional mechanical support, including crystals, silicon glue or any other compound. 8) Soldered or connected wires and cables should have a nylon clamp to hold them firmly to the board, avoiding movement at the solder or connector point. You simply can't find ruptured wire filaments in cables and wires clamped on. 9) Protect all your board and components, immerse it in a heavy coating if possible. If everything is nice and clean, probably you will never need to repair that board in life. 10) Cross your fingers and Pray a lot. The general answer for bullet proof circuit: Shield it in 5 inches tick Plexiglas box with extra half inch tick kevlar vest around. -------------------------------------------------------- Wagner Lipnharski - UST Research Inc. - Orlando, Florida Forum and microcontroller web site: http://www.ustr.net Microcontrollers Survey: http://www.ustr.net/tellme.htm