F3F TIMER PROJECT by Jon Edison
Updated Feb 2017
MK III Construction Details
( Additional Components here )
Both the PCB design and Component Layouts are shown below.
The PCB is shown Full Size.
This design allows for easy home construction as all the components are 'through hole' mounted, no surface mount technology is used. Components are available from suppliers such as Maplin, Rapid Electronics and RS Components. A pre-programmed processor ( IC3 ) and FREE PCB are available from the author for £25.
Produce the PCB using a photo etch process. Drill all holes 0.8mm. Open up the holes shown in red to 1.0mm. Blue holes to 1.3mm, and Green holes to 3mm.
Start with C13 and the Link under IC3. Make sure C13 is as close to the pcb as possible. Install the 28pin DIL socket over the link and C13.Then install the remaining larger components such as BR1, C4, VREG1, OPTO1, 2, and 3, IC1 and IC2. These give a guide to the positions for the remaining Resistors, Capacitors and Diodes. Finish off with the Molex and other components . Finally, mount IC3 in the 28pin DIL Socket.
Check and check again that there are no solder bridges between tracks, and all IC's and Diodes are the correct way round. Wire sockets SKT10 and 11 to the board with short lengths of cable. Check with a multimeter that no short exists on the board by placing the meter set to continuity / resistance across these sockets. If all is well, a reading greater than 500K ohm will be obtained. Now set the multimeter to its Current setting and place the meter inline with one of the input wires. Apply a voltage of between 9 and 12 volts to the board via the multimeter, a reading of approx 30mA ( 60mA if the IOIO board is attached ) will be shown, and LED1 will be lit. Recheck if readings are seriously higher than these. Otherwise you have successfully produced a working timer which can now be mounted in its case.
Drill the case as shown. The PCB is designed to be held in position by SKT3 and 4. After testing, slip the board into the case, sockets first, then tighten the two nuts on the sockets to securely hold the board. Mount SKT10 and 11, and connect to the board. Install and connect Sockets SKT7 and SKT9. Finally connect the IOIO board to the main pcb, and mount on the 3 nylon pillars. NB the IOIO board shown is the recommended V1 board. Later versions have a smaller USB connector.
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