Price - Stock No 190 - Flying Lead Input 
Price - Stock No 191 - 12V Accessory Plug Input 


This kit provides a charging source for USB devices.


  1. Check  the  P.C.Board  for  damage to tracks.  Any breaks can be soldered over.  Check with a multimeter or electronic circuit tester.
  2. Identify the resistors, see Resistors.
  3. Solder in place - see Soldering Technique.
  4. Examine the 7805, note the pin names and orientation from the above diagrams.  Bend the legs of the 7805 so that it lies flat on the PCB.
  5. Insert the 7805 and solder.
  6. Insert the USB socket, making sure all pins and mounting lugs penetrate the PCB.
  7. Using pliers fold the lugs to secure the socket.  Solder the lugs to the PCB. 
  8. Solder the 4 pins of the USB socket.
  9. Insert and solder the two PCB pins.
  10. Identify the capacitors, the 100uF electrolytic is polarised and must be inserted in the correct orientation. Solder.
  11. The 0.01uF greencap is not polarised.  Insert and solder. 
  12. Identify the legs on the LED.  Ensure it is inserted with the correct polarity and solder.
  13. Strip and tin the ends of the figure 8 wire.  See Tinning Wire
  14. Connect one end of the wire to the PCB pins.

Operation and Testing

Take Care - the 7805 will dissipate heat.  Temperatures in excess of 70 oC can be expected when charging. 

  1. Apply the correct voltage to the input.  The LED will illuminate.
  2. Check the USB output socket - Using a multimeter, black lead on GND (Pin 4), measure the voltage on the other pins of the USB socket.  5V on each pin is correct.
  3. Attach your USB device, charging will occur.


Technology Notes

This circuit uses a 7805 voltage regulator to provide a constant 5 V source.  The 7805 is supported by the two capacitors.

The regulated 5V is provided to the USB device at pin 4.  The data lines pins 2 & 3 are biased high through the 10K resistor.

The 220R resistor limits the current through the LED to an acceptable level.

Trouble shooting

Troubleshooting,  if necessary will involve careful checking of locations and polarity of components, in particular the diodes and the SCR. Re-solder all joints and check to make  sure  you  have  not  bridged across  between  any  two adjacent component legs.  The end  of  a  broken  hacksaw  blade  sharpened  on  an  emery wheel is a good tool for cleaning between soldered joints.

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