Hi: I've added a photo of the component side of the 8051 PCB at: http://www.prc68.com/I/ThunderBolt.shtml#8051PCB
J1-2 is connected directly to pin 6 of the uC which is also connected to the output of the 78D05 regulator.
Have Fun, Brooke Clarke http://www.PRC68.com [email protected] wrote:
Hi All As there still seemed to be unanswered questions regarding the circuitry of these I've separated the two PCBs from one of mine to determine exactly what is going on. Whether or not the regulator circuit is based in any way on the iCruze original processor board I don't know but it's now quite clear that the processor circuitry itself is an amost exact copy of Didier's version using the 20 pin DIP C8051F330 processor. The only differences I've found so far are the values of the resistor in the programming interface and those on the RS232 input but the layout itself looks to be identical. I'll go over it more thoroughly later and produce a complete schematic. Didier's original schematic, which includes the three series diodes for use with a 5 volt supply, can be found here ..... _http://www.ko4bb.com/Timing/GPSMonitor/Schematic-3.png_ (http://www.ko4bb.com/Timing/GPSMonitor/Schematic-3.png) As commented by Leigh earlier, all the diode positions on the PCB are occupied by zero ohm links so I think it's reasonable to assume this is probably universal and ALL monitors are likely to need modifying to keep the processor supply voltage at a safe level. The absolute maximum rated supply voltage is 4.2 volts, IO port and RST pins are indicated as tolerating up to 5 volts, but the specified operating supply voltage range is 2.7 to 3.6 volts so I would recommend fitting all three diodes as per Didier's original circuit rather than just two. The supply to the display is taken directly from the output of the regulator and not via the diodes. For anyone wanting to avoid hardware modification another option would be to run the unit from an external 5 volt supply, as was originally suggested, and let the onboard regulator just act as a dropper. With a 5 volt supply the output voltage from the regulator is 3.6 volts but of course it isn't regulating and the supply to the display is also reduced. I have found that my display at least will run ok at 3.6 volts but the contrast pot may need adjusting. However, if this route is followed there's little room for error and it's important to make sure the external supply is kept below 5.6 volts otherwise the processor supply will again exceed 4.2 volts. Fitting the diodes is a once and for all solution and is certainly the preferred option. regards Nigel GM8PZR _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
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