PDF《DIY KIT 141. Multi-Mode Timer》

3 - Delayed On Trigger signal starts the timing cycle. At the end of the delay time the relay operates and stays operated until the trigger signal is removed or the timer is reset. Loss of trigger signal during the delay time aborts the timing cycle. Mode

4 - Instant On and Hold, Delayed Off Trigger signal operates the relay but does not start the timing cycle. The relays remains operated while the trigger signal is present. Loss of trigger signal starts timing cycle. Relay releases at end of delay time. Mode

5 - Toggling Trigger signal operates the relay for selected delay time. The relay then releases for the same delay time. This cycle continues until loss of trigger signal or reset. Mode

6 - Instant On, Delayed Off, with Pause Similar to Mode

0 C a trigger signal operates the relay and starts the timing cycle. However, loss of trigger signal causes the timing cycle to pause C the relay remains operated. Re-applying the trigger signal will re-start the delay time from where it was stopped. At the end of the delay time the relay releases. DIY KIT 141. Multi-Mode Timer Page

2 Mode

7 C Delayed ON with Pause Trigger signal starts the timing cycle. At the end of the delay time the relay operates for

2 seconds and the timing cycle starts again. Loss of trigger signal causes the timing cycle to pause. Re-applying the trigger signal re-starts the timing cycle from where it was stopped. Reset is the only way to exit this mode. Mode

8 C Unused NOTE: For each of the timer modes a reset signal will stop the timing cycle immediately and reset the timer, ready for another trigger signal. The timer is reset by connecting the RST input to the GND input. ASSEMBLY INSTRUCTIONS Use the component overlay on the PCB to place the components starting with the lowest height components first. Make sure that the diode, LED and electrolytic capacitors are inserted the right way around. A heatsink is fitted to the

7805 regulator using the supplied 3mm screw and nut to bolt the assembly to the PCB. Before tightening make sure the heatsink is not touching the relay. The SIL resistor network has a small '

dot'

at one end. This end should be next to pin

20 of the Atmel micro There are two 5-way screw terminal blocks on the board. These are made by fitting together a 2-way and 3-way block, sliding the raised edge on the side of one block into the matching groove of the other block. The terminal block is inserted with the '

wire opening'

to the outside of the PCB. They are rated 300V, 10A. Do not insert any ICs yet. TESTING Apply power to the board. The RED power LED should be on and the relay released. Use a multimeter to measure the voltage across pins

20 (+) and 10(-) of the IC2 socket C it should read

5 volts. Use a short length of wire to connect IC2 socket pins

10 and 11. The relay should operate. If all is well remove power and insert the ICs. Make sure no IC leads are '

bent under'

as you insert them. CIRCUIT DESCRIPTION The heart of the circuit is IC2, an Atmel 89C2051 microcontroller. This is a 20-pin device using the popular

8051 core. It is pre-programmed with software to provide all the timing functions. A 12MHz crystal provides accurate timing and an easily divisible clock source for the internal hardware timers. The source code for this kit is not available. Timing Accuracy: Crystals are accurate to +/-

100 ppm (parts per million). In this case the actual crystal frequency could vary by as much as 1200Hz either side of 12MHz - an error of 0.01% maximum. Over 42.5 hours (2550 minutes, the maximum delay time this kit can be programmed for) this amounts to a maximum error of +/-0.255 minutes (+/- 15.3 seconds). Try getting that with an RC circuit! The trigger signal is applied to the input of IC1, a 4N25 optocoupler. Using an optocoupler allows the trigger signal to be electrically isolated from the timer kit. This is especially useful if triggering the kit from high voltages such as mains, etc. Diode D2 protects the optocoupler'