Making the LED Battery Monitor Board (Optional)

We are also including a neat little LED battery monitor board for you to make BUT it's purely optional. It's purely there to let you know the state of the 12v battery!! As long as the battery has over 11.6 volts the green led stays on..once it drops below that level the red led comes on warning you that the battery will need recharging soon!! For those "techheads" who can make stuff directly from a schematic..it's the one above for you to use. If you however need step-by-step instructions on how to make this board...keep reading and we will make one together.
Now, you will have plenty of Veroboard left over from the voltage regulator so make a new piece of board 5 strips deep and 13 holes long. On this board we need to break the strip in 4 places so using a drill bit in your fingers, clean away B4, C4, C9 and D9 holes so your board looks like the one in the image above.
Right!! let put in the components and solder them. Grab the red led and put into holes A2 and B2 BUT wait a second...it has to be the right way around otherwise it won't work!! If you look carefully you will see the led has one lead shorter than the other which is called the cathode...so the cathode lead must go into hole B2 and the anode lead (the longer one) will go into hole A2. Also don't push the led all the way in...let it stick up from the board around half an inch...that way both leds will be a head and shoulders above all the other components and you will be needing them to protrude a little more when they are mounted in the case. OK, you can now solder both points and trim off the excess lead.
Ok?? let's move on. Now get a 1K ohm resistor and place in into holes B3 and C3 (resistors can go anyway around) Solder both points and trim the leads and it should look just like the images above.
Now get one of the BC547 transistors and let's mount that. Transistors DO need to be the correct way around and this is really easy as the body has a flat face on it. Insert the device into holes C2, D2 and E2 making sure that the flat face faces towards the end of the veroboard as shown in the image above. Then again solder each of the 3 leads and trim off the excess leads so it looks neat.
Right, next we need to find your 100k ohm resistor and insert it into holes C5 and D5 ... any way around it fine...solder each lead and trim off the excess.
Now, let's add the 2nd LED ...remember that it has to go the correct way around!!! so insert the green LED into holes A7 and B7 making sure that the shorter lead goes into the B7 hole and the longer one into the A7 hole..Again, don't push the led right down but leave it sticking up about 1/2" from the board so it's around the same height as the RED led . Solder both leads and trim them off.
Ok??? now look for the other 1K ohm resistor and insert it into holes B6 and C6 ( again any way around) and solder the leads and then trim them off.
Now it's time to add the second transistor, also a BC547... insert it into holes C7, D7 and E7 making sure the the flat face is facing the same way as the first transistor ..check the image above if you are not sure!!! Great!! now solder the three leads in place and trim off the excess!!
Ok??? Now find the other 3.3K ohm resistor and put it into holes D8 and D10 (again any way around). Solder the leads and trim them off.
Now let's put in the very last resistor which is also a 3.3K ohm same as the above one but this time it goes into holes D11 and E11. Again solder the leads and trim them off. We are nearly done now..just a few more!!
You now need to find the 10 v Zener diode and if you look at it carefully it has a black band on one end ..this is the cathode. Put the cathode end (with the black band ) into hole C12 and the other end into hole D12 and then solder both the leads and trim them off.
OK, last component is the IN4148 diode... look carefully and you will see this also has a black band at the cathode end. Put this end into hole C13 and the other into A13. Solder both leads and trim them. That's the lot.
However we have just one more tiny job to do!! Take some thin red and black cable and solder the RED wire into hole A1 and the BLACK into hole E1.
That's your LED monitor complete!! If you connect the end of the red wire to the battery "+" and the black to the battery "-" the green LED will light up and when it's almost flat the red LED will come on Click the Step 4 link below Back to the previous Page STEP 4 - Assembling your Extended Power Pack