In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote: Well you need the on and off of the SX to responsd to hysteresis. I suspect an Op Amp configured to the taylored needs of the solar cell would be a good choice. In this way, it would go down below the off level before cycling into a recovery and then charge to a higher voltage than minimally needed before turning on. If you want to complete the trick, I have an odd little 4-wire 3.3 volt/ 1 amp voltage regulator, that would be ideal. The fourth wire turns the output on and off. In fact, you might be able to use it without bothering with an external op amp. You might be able to use a zener diode and resistor. Take a look at the Farichild KA78R33 Low dropout voltage regulator. I suspect it might also eliminate the need for blocking diodes, but that depends on where you put the supercap [before or after the regulator]. The 1 amp rating maybe a bit of overkill. One senario with a blocking diode is to put the supercap before the regulator, have the regulator trigger appropriate full on and off, and then put a large-ish storage cap after the regulator - say 1000mf. This particular regulator wants greater than 47mf on the supply side for smooth operation. Have a protective diode running in the reverse of normal current flow from the output side to the input side. I would be interested in trying to include an Ultra low power RS-422/485 transceiver to moves data over distances. But in reality, I don't think one could get more than 10-20 seconds out of a 1 farad supercap when using a BS2 alone. Most of the time you would be relying on the KA78r33 to manage staying power and it may be very important to protect it from back current. But in theroy if the supercap on the supply side is bigger than the regulating cap on the output side, no damage would occur. A 7805 can be damaged by anything larger than 10mf if suddenly unpluged with a protective diode and it is its documentation which brings me to be concerned. The KA78r33 shuts off when the monitored input voltage is below 1.4volts. It can be adapted to turn on at 1.4volts or anything higher. Since this is an op amp input, it takes very little current away from charging the supercap before power is turned on. You could have another voltage monitor provide early warning of voltage drop to provide orderly shut down. Beam Robotics builder use a little 3 wire device. If you tie the trigger to the RTCC, it can call a shut down routine. If that is no good, any of RB port can provide an interrupt. You've fired my imaginations. I forgot about these regulators. Originally I got stuck with them because they were the only 3.3volt regulators in town and I had considered the 4th wire a hassle. Now I begin to see it as real neat. ---------- End of Message ---------- You can view the post on-line at: http://forums.parallax.com/forums/default.aspx?f=7&p=1&m=221843#m222046 Need assistance? Send an email to the Forum Administrator at forumadmin@parallax.com The Parallax Forums are powered by dotNetBB Forums, copyright 2002-2007 (http://www.dotNetBB.com)