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Sunday, November 25, 2007

Assembling A FLED Solar Engine Tutorials

1. Take the 3904 transistor and using a pair of long nose pliers carefully bend the collector leg (that's the one on the far right) so that it is perpendicular to the transistor body as shown in the photograph. Then again using long nose pliers carefully bend the emitter leg (the one on the far left) first perpendicular to the base leg (the middle one) but in the same plane and then back up towards the base leg as shown in the photograph. If you're not sure about this take a look at step 3 and 4 it might be clearer when you can see the assembled engine.

2. Take the 3906 transistor and bend the emitter leg (the one on the far right in the photograph) first perpendicular to the base leg but in the same plane and then over the top of the transistor body. Then take the base leg and bend it perpendicular to the transistor body as shown in the photo.

3. Hold one of the transistors with a pair of long nose pliers so that the base leg of the 3904 is next to the collector leg of the 3906. The legs should overlap by about 6mm - 8mm. With your other hand pick up your soldering iron (which should be hot !), clean the tip and then melt a little pool of solder on the tip. Apply the tip of your iron to the two legs of the transistors to be joined for a second (no more !). The legs will be heated and the solder should flow between them easily. Do not overheat (it may damage the transistors). Continue to hold the transistors together for about two seconds until the solder has solidified.

Now wipe the sweat from your brow!

4. Solder the 2.2k resistor between the collector leg of the 3904 and the base leg of the 3906 as shown in the photo. This is best done by first 'tacking' both ends of the resistor to the transistor legs with a small pool of solder on the iron and then applying additional solder to make a more secure joint, once the initial 'tack' has solidified. Using a pair of side cutters trim the excess lead from the resistor.

Almost there !

5. Carefully bend the negative leg (the shortest one and also the one nearest the 'flat' on the FLED body) of the FLED at right angles to the positive leg, as shown in the photo.

6. Slide a piece of heat shrink tubing over the FLED and using a lighted match shrink the tubing over the FLED body. Whilst the tubing is still hot pinch the end opposite the leads to seal the tube, then cut off any excess tubing.

7. Solder the negative lead of the FLED to the emitter of the 3904 (the one that is bent backwards) and the positive lead to the base of the 3906 (to which the resistor is also connected)

8. Trim off the excess leads : FLED negative, FLED positive and 3906 base - as shown in the photo


Anonymous said...

I have a question and you may be able to help. i'm assembling my FLED SE without a solar cell, its in the mail so i'm bench testing with 2 AA batteries. my FLED SE seems to be working, but the LED keeps flashing after the transistors 'switch'. I can remove the LED and the switch stays open. so i know the switch is working. so i'm looking for some clarification about how the LED should function. Should the LED flash at all or only when it activates the 'switch'?

Anonymous said...

Good question. I don't know the answer. I just built my first symet yesterday. I prototyped everything on a breadboard and it worked under the light of a lamp in my house.

Now that I've fully assembled everything, it doesn't work under the lamp. The motor has a high pitched whine and according to the book that means I should use a smaller resistor. So I swapped the 100k resistor for a 1k resistor. The whine is gone, but it still won't run under a lamp.

When I take it outside to full sunlight, it comes on and stays on until the solar panel points away from the sun. It doesn't pulse like it did under a lamp when it was all breadboarded together.

Fortunately, I bought enough materials (except motors) to build a couple more so I can try again.