An Automatic Re-Booter for your Board by Matthew Lewis Sysop of Media Shack PCBoard Toronto, Ontario, Canada (416) 699-1846 þ 300-2400 bps Background: This came about because of a couple of events that for some reason didn't successfully complete, and the board failed to reload, leaving my board down for most of the day until I retured home from work. I originally connected a telephone answering machine to the board's phone line, and set it to answer on the fourth ring. As the board normally answers on the first or second ring, under normal conditions, the answering macnine would do nothing, but if the board failed to answer the phone, the machine would answer on the fourth ring, play a tape to the caller advising him to wait about a minute and call back, and reboot the computer. The last commands in my AUTOEXEC.BAT file would reload and start the board program. After some proding by some other sysops who heard about this, and wanted one themselves, I designed the circuit described below. I have designed this circuit so that it can be built from parts which should be available at any Radio Shack store, not because of any particular fondness for Radio Shack, but just because this will virtually guarantee availability of the parts anywhere. The total cost for all required parts should be less than $20.00. Parts List: You will need the following parts. 2 - Opto-isolators similar to Motorola 4N36 1 - Operational Amplifier or Comparitor IC (741, 1458, TL082, LM358, etc.) (I used an LM358J) 1 - Silicon Diode - Virtually any will do (D1) 1 - 100 nF (0.1 uF) capacitor - min 100 volt rating (C1) 1 - 470 uF capacitor - min 16 volt rating (C2) 1 - 680 ohm 1/4 watt resistor (R7) 1 - 1,000 ohm 1/4 watt resistors (R2) 1 - 10,000 ohn 1/4 watt resistor (R1) 2 - 100,000 ohm 1/4 watt resistors (R4 & R5) 1 - 22,000 ohm 1/4 watt resistor (R3) 1 - 20,000 ohm multi-turn trimpot (R6) 1 - piece of perf-board to build it on misc wire and hardware for mounting That's it for the parts you'll need. Now on to my attempt at a schematic diagram. Schematic Diagram of Auto Re-Booter + 12 v ³ Line 1 ÚÄÄÄÄÄÄÄ¿ ÚÄÄÄÄÄÄÄÄÄÄ¿ ³ ÄÄÄÄÄÄÄÄÄ´ C 1 ÃÄÄÄÄÄÂÄÄÄ´a cÃÄÄÄÙ ÀÄÄÄÄÄÄÄÙ ÚÄÁÄ¿ ³ ³ ÃÄÄÄ´ ³ Opto- ³ ³D 1³ ³ isolator ³ ³ ³ ³ ³ Line 2 ÚÄÄÄÄÄÄÄÄ¿ ÀÄÂÄÙ ³ ³ ÚÄÄÄÄÄÄÄÄ¿ ÄÄÄÄÄÄÄÄÄ´ R 1 ÃÄÄÄÄÁÄÄÄ´k eÃÄÄÄÄ´ R 2 ÃÄÄÄ¿ ÀÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÄÄÙ ÀÄÄÄÄÄÄÄÄÙ ³ ³ ³ ÚÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÂÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ³ ³ ³ ÚÄ¿ ÚÄÄÁÄÄ¿ ÚÄÁÄ¿ ³ ³ ÀÄ¿ + 12 v ³ C 2 ³ ³ ³ ³ ÚÄÄÄÄÄÄÄ¿ ³ ÀÄ¿ ³ ³ ³ ³R 3³ ÀÄÄÄ´ R 4 ÃÄÄÄÄÄÄ´ + ÀÄ´ ÀÄÄÂÄÄÙ ³ ³ ÀÄÄÄÄÄÄÄÙ ³ ÀÄ¿ ³ ÀÄÂÄÙ ³ Op-Amp ÃÄÄÄÄÄÄ¿ G G ÚÄÄÄÄÄÄÄ¿ ³ ÚÄÙ ³ ÚÄÄÄÄÄ´ R 5 ÃÄÄÄÄÄÄ´ - ÚÄ´ ÚÄÁÄ¿ ³ ÀÄÄÄÄÄÄÄÙ ³ ÚÄÙ ³ ³ ³ ³ ³ ÚÄÙ G ³R 7³ + 12v ³ ÀÄÙ ³ ³ ³ ³ ÀÄÂÄÙ ³ ³ ³ ÚÄÁÄ¿ ³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ ³ ³ ³ ³ ³R 6³ ³ ³ ÚÄÄÄÄÄÄÄÄÄÄÄÄÄÄ¿ ³ ³<ÄÄÄÄÄÙ ³ ³ ³ to Reset Switch + ³ ³ ÀÄÄ´a cÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ ³ ³ ³ ³ ³ ³ Opto- ³ ÀÄÂÄÙ ³ isolator ³ ³ ³ ³ G ³ ³ to Reset Switch - (G) ÚÄÄÄÄ´k eÃÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ ³ ³ ³ G ÀÄÄÄÄÄÄÄÄÄÄÄÄÄÄÙ Notes: Opto-Isolators a = anode of LED k = cathode of LED c = collector of transistor e = emitter of transistor G = ground connections Op-Amp + = non-inverting input - = inverting input Theory of operation: When the phone rings, a voltage of about 80-90 volts, peak to peak, aproximating a square wave, is placed on the line. This signal is passed by capacitor C1 and resistor R1 to the LED of the first opto-isolator causing it to light on one half cycle. Diode D1 is there to conduct on the other half cycle. During the time that the LED is forward biased, and lighted, the photo-transistor will conduct, charging capacitor C2 through resistor R2. When the phone is not ringing, capacitor C2 will discharge via resistor R3, at a slower rate that it is charged at while the phone is ringing. The voltage on C2 is coupled to the non-inverting input of the op-amp via resistor R4, and when it becomes more positive (by just a couple of microvolts) than the voltage at the wiper of R6, then the output of the op-amp will rise to about 10.5 volts, causing the LED of the second opto-isolator to be forward biased, and lit, causing the photo-transistor to conduct, and the computer will re-boot just as if you pressed the reset button. Trimpot R6 is adjusted for the Op-Amp output to go positive after the desired number of rings. In my own case, I found that when the voltage at the wiper of R6 is set to 7.5 volts, with respect to ground, the computer will reboot on the fourth ring. The higher the voltage on the wiper of R6, the more rings it will take before the computer reboots. CAUTION: I am using this device on an XT clone, but have been told by someone else who tried a similar idea on an AT, that if the reset button is pressed a second time before DOS gets loaded, it will go into the CMOS setup, and wait for input from the keyboard. I have no way to test this, so if you're using an AT or clone, try hitting the reset button again before DOS gets loaded to see what happens, BEFORE INSTALLING THIS DEVICE! DISCLAIMER: I make no guarantee what-so-ever that the above described device will work for you, or meet your phone company's acceptance. Furthermore, I will not be responsible in any way for any loss of any kind that you may suffer because of using this device. The ONLY claim that I make is that I have used the above described device on my own system, and it works for me. Closing Statement: I hope that you will find this device usefull, and if you do, I would appreciate a note in either the InterLink or CanConfMail/SmartNet Sysop conference. Matthew Lewis - Sysop - Media Shack PCBoard Toronto, Ontario - (416) 699-1846