Just an FYI for those who want to build themselves a tach booster and dont know where to get the parts.
Visit your local Jaycar Electronics store and purchase the following:
- ZT2115 - BC337 transistor - $0.42
- ZR1007 - 1N4007 diodes, pack of 4 - $0.60
- RR0582 - 2k7 resistors, pack 8, $0.46
- SY4068 - SPST 4-pin relay, $7.95
- PT4525 - red female spade crimp terminals, pk 8, $2.75
- WH5532 - 3.0mm black heatshrink, $1.85
- WH5533 - 5.0mm black heatshrink, $1.95
- WH5554 - 6.0mm clear heatshrink, $2.25
Now im too lazy to bother opening up a relay and doing some finicky soldering to the guts of it..... so i did an external version
METHOD:
- Start by soldering the 2k7 resistor and 1N4007 diode together. Pay attention to the diode - the grey band should point towards the resistor
- Now solder the other end of the resistor to the base (B) leg of the BC337 transistor. Note the pinouts of the BC337 below
- Solder wires to the other two legs of the transistor. "E" of the transistor goes to earth, "C" of the transistor goes to the tacho output and also the relay coil.
- Attach spade terminals as follows, and connect to your relay.
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