Step-by-step instructions
Here are step-by-step instructions on how to make the 12V LED turn signal setup described in the first post. These instructions aren't designed for understanding the circuit; they're really just for helping people put the pieces together properly. Let me know if you have questions.
1. Go buy:
- 2x 12V LED modules of your choice. (don't get too crazy here - the circuit is designed for a generic LED setup, not a 4,000,000-lumen LED searchlight...)
- 2x
RFD3055LE N-channel Mosfets from Digikey.com. (0.79 USD each)
-datasheet here-
- 1x
CD4047BE Multivibrator from Digikey.com. (0.48 USD each)
-datasheet here-
- 2x DPDT switches of your choice (what you'll be switching to turn on and off the turn signals). Radioshack is a good bet. They can be bought from Digikey, but I like to see/feel a switch before I buy it.
- 1x
100uF electrolytic capacitor - go to RadioShack, or tack one onto your Digikey order
- 1x
2-3 kOhm trimpot/potentiometer/variable resistor/whatever else you'd like to call it. Nothing fancy here. I'd get one for $0.50 at Radioshack. Will probably have 3 pins, but might have only 2.
ORDER EXTRAS - THEY'RE CHEAP! If you've never soldered to integrated circuits before, you should
definitely buy extras. Prolonged exposure to the soldering iron's heat can damage them, so be careful!
2. Solder pins 4, 5, 6, and 14 of your CD4047BE together (see diagrams), and solder a wire coming off of one of these pins. These pins will all be connected to +12 V eventually. Check for continuity of these connections using a multimeter in resistance-measuring mode. Put one multimeter probe on the free end of the wire, and move the other probe from pin to pin. The resistance measurements should be 0 ohms or very small (<<10 ohms).
3. Solder pins 7, 8, 9,and 12 of your CD4047BE together, and solder a wire coming off one of these pins. These pins will all be connected to 0 V (GND, the negative side of the battery) eventually. Again, check for continuity of these connections with a multimeter.
4. Determine the pinout of your trimpot/potentiometer/etc. Basically, you need to use your multimeter to identify two pins (normally of three pins total) between which the resistance changes when you twist the knob. Normally this is the middle pin and either of the two outer pins. By spinning the knob, you should be able to change the resistance you're measuring from ~0 ohms to the max for your potentiometer (probably 2-3 kOhms).
5. Solder one of these two pins on the potentiometer (you identified these in the previous step) to pin 2 on the CD4047BE, and solder the other pin to pin 3 on the CD4047BE. You may want to use wire for this, you may not.
6. Identify which one of the two pins on your 100 uF capacitor is the positive pin. If you didn't buy an electrolytic capacitor, don't worry about this step. If you did buy an electrolytic capacitor, one of your capacitor's lead wires is probably longer than the other one. This is the POSITIVE one. Also, there may be markings on the plastic wrapper of your capacitor indicating the lead polarity. In my original schematic (from the first post), you will notice that half of the capacitor is shown as curved, while half of the capacitor is shown as straight. The curved side of the capacitor is the negative side, and the flat side of the capacitor is the positive side.
7. Solder the POSITIVE lead of the capacitor to pin 3 of the CD4047BE, and solder the NEGATIVE lead of the capacitor to pin 1. You will note that your potentiometer is also soldered to pin 3 (step 5). Try not to damage the solder connection you already made.
8. Make sure you know which pins are what on your two Mosfets. These are labeled with "S" (source), "D" (drain), and "G" (gate) in the images I attached to this post.
9. Using wire, solder the G pin on each of the Mosfets to pin 10 on your CD4047BE.
10. Using wire, solder the S pin on each of the Mosfets to the connection you made earlier between pins 7, 8, 9, and 12 on your CD4047BE (step 3).
11. Solder the negative wire of one of your LED modules to the D pin (middle pin) of one of the Mosfets. Also do this for the other LED module and the other Mosfet.
12. Use a multimeter in resistance-measuring mode to determine the operation of the six pins on each of your DPDT switches. You really need to understand how a DPDT switch works in order to do this. In general, the two middle pins are the throws, and the four outer pins are the poles. If you're having trouble with this part, post a question.
For each of the two switches:
- Throw #1 should be soldered to ground.
- Throw #2 should be connected to +12 V on the battery.
- When the switch is in position A (arbitrarily assigned), throw #1 should be connected to pin D of one of the Mosfets. Throw #2 should be connected to nothing.
- When the switch is in position B (the OTHER position
), throw #1 should be connected to nothing. Throw #2 should be connected to the connections you made between pins 4, 5, 6, and 14 on your CD4047BE (step 2).
13. Finally, connect the positive wire of your LED module to +12V on the battery.
-- I almost forgot to mention that if your turn signals are flashing really quickly or really slowly, you need to twist the knob on the potentiometer until they flash at a speed you like.
-- Also, as an optional suggestion, I usually cover the small, fragile connections between components in a hefty layer of hot glue when I'm done. It protects the solder joints both from shorting to other metal objects and breaking under stress. Just be sure your circuit is working before you do this
.
All of these connections should be identical to what is drawn in the original schematic, so if you're having trouble conceptualizing what it should look like, head there.
Good luck!
-Rock
(sorry I picked such a long name when I joined... "Rock" is much easier to type, lol.)
