How to make a simple low cost LED Flash Circuit
From the start I HATE soldering! Luckily this project isn’t too bad. The circuit can be made easily on a readily available PCB and the actual placement of the components is very similar to the circuit diagram making things a bit easier to follow. So here is the circuit.
To see how the circuit fits in to the rest of the tanks wiring refer to the pictures in the Upgrading a Pz III Topic located .
There may be occasions where a Flash LED is a better option than the High Voltage Flash unit. In particular if a scale barrel for the Pz III is used as a 3mm LED will fit down the barrel. This unit is actually cheaper than the High Voltage flash to construct and with a 5 mm high intensity LED will do a fine job down a Tiger or any other larger barrel.
Below is a list of parts you will need, their Jaycar catalogue number and cost at time of writing. Apart from the experimenters board they are common, readily available, cheap components that you should have zero problem sourcing elsewhere.
Parts List
1 x Ultra Mini Experimenters Board (HP9556) $4.95
1 x NE555 Timer Linear IC (ZL3555) $1.25
1 x 1uF 63V RB Electrolytic Capacitor (RE6032) $0.34
1 x 100 nF 50V Ceramic Capacitor (RC5360) $0.36 (Pk of 2)
3 x 100K 0.5 W 1% Metal Film Resistors (RR0620) $0.46 (Pk of 8 )
(NB: The resistors come in packs of 8 from Jaycar so you need only buy 1 pack)
Total cost is less than $7.50. However you will only need 1/8 of the experimenters board and hence you will be able to make up to 7 more circuits for about $2 each. Alternately you can use the some of the leftover board to make an Anti-Track recoil circuit (instructions later).
Preparation
First thing to do is snap the Experimenters board in half and then cut one half into quarters as shown below.
IMPORTANT: For this guide use the bottom left corner of the PCB. You may wish to trim the excess board at this point so that your board is as small as possible. Test fit the components as shown below.
Construction
To help follow these instructions I have assigned each of the holes in the PCB a grid reference. Horizontally the holes are labeled A to J from left to right and vertically from Zero to 7. Hence the hole in the bottom left corner is (A, 0) and the top right hole is (J, 7). R1 is placed into holes (A, 2) and (A, 7). I have left this numbering system off of the pictures for clarity.
Step 1
Solder the first of the three resistors to the PCB and cut off the excess wires. The LM55 Timer IC is soldered into position next.
Step 2
Solder the second resistor in place, cutting the excess wire when done. With a short section of this wire, form, cut and solder in place wire 1 (W1).
Step 3
Form, cut and solder in place wire 2 (W2). The soldering of R2 is a little bit more tricky that usual. One wire goes into (E, 7) the other wire goes first into (E, 6) then is bent to come back out of (F, 6), bent again to go back down hole (H, 6). A sort of rabbit goes down the hole back up another hole and then down again in yet another hole.
Step 4
Form, cut and solder in place wires 3, 4 & 5.
Step 5
The installation of C1 is also a little different to normal. Cut a small length of wire and solder to one pin of C1. Place this pin into (C, 1) and the other pin into (A, 1). The end of the short wire goes into (E, 1)
Step 6
Move aside wires 5 & 6 to expose the mounting holes for Capacitor C2. Solder in place C2 (NOTE the negative pin of C2 goes into the hole (H, 0) at the bottom of the board).
Step 7
Connect the pair of input wires from the 8-Pin connector as shown with the positive wire going to (B, 7) and the negative wire to (A, 0). Now connect an output pair of wires for your selected flash LED, positive wire to (J, 1) and the negative to J, 0). Finally, turn over your PCB and break the connection at A using a sharp hobby knife. Check your soldering and make sure that there are no unwanted connections between the traces, the exception being at B where the excess wire of R2 is used to connect pins 6 & 7 of the 555 timer.
For the most part the circuit is now complete. You can either place some shrink wrap over the board or use some insulation tape to avoid any possible short circuits. To complete the circuit you will need to decide on what type of LED you wish to use. What LED you use will determine the value of the resistor that you will need to place inline with the LED. Once you have chosen your LED you will need to know its operating voltage and current. You can then go here:
http://www.quickar.com/noqbestledcalc.htmor
http://led.linear1.org/1led.wizto calculate the required resistor. For example if you get a 20 milliamp 3 volt LED you will need a minimum 100 ohm resistor.
Supply Voltage = 5 volts
Voltage Drop across LED = 3 volts
Desired Current = 20 milliamps
Fini
