Extensible Multiple Device Programmer 4 Base

  
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The 5 volt microcontroller interfaces to the RS-232 serial connector and the USB-B connector. It is also responsible for talking to the checker, controlling the status LED`s and setting the voltage for the LOW voltaage microcontroller. The low voltage microcontroller is run at the voltage level appropriate for programming the device to be programm
Extensible Multiple Device Programmer 4 Base - schematic

ed. It has direct control over a 24V DAC and a 8V DAC. The customization plug is just a large number of female pins for routing power and signals to the 40-pin ZIF socket. One half of the customization plug is hooked to the low voltage microcontroller. The power supply uses a Underwriters Labratory ® approved "wall wart" to provide 24VDC of power. This means that the base board does not have any 110 AC or such voltages running around on it. The power comes in on either N1 (on board) or N3 (off board). The power switch can either be on board at SW1 or off board as SW2 through connector N2. A resettable polyswitch fuse is used to deal with short circuits at F1. D1 is a shorting diode that should trigger F1 if somehow a VAC power source gets plugged into N1 or N3. The rest of the power supply a series of inexpensive linear voltage regulators, VR1-VR5, that step the voltage from 24 volts, to 18 volts, to 12 volts, to 8 volts and finally to 5 volts. All of these supplies are used elsewhere on the board except the 18 volt one, which is used to keep the 24 volt regulator, VR1, from disapating too much heat. The capacitors are tantalum for their low series resistance. This design will not win any energy conservation awards, but since the EMPD3 should spend 99% of its time turned off, there should be no real complaints. Finally, green LED D2 lights up to indicate that the device is turned on. The EMDP4 is a board that uses standard...



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