information and inspiration
for students, teachers and hobbyists
About Tools Products Activities Galleries Projects Links Contact Facebook LinkedIn  flickr


Assembly and Operating Instructions for Kits


Instructions for Preparing a Flash Trigger Cord (PC Kits)


Assembly instructions for other kits



These instructions are for connecting the output of a breadboard trigger circuit to a flash unit using a PC cord. The flash unit must have a PC jack that will accept a standard PC plug. A typical jack and plug are shown in Photos 1 and 2 below. Click on either image for a larger view.




Photo 1. Flash with PC jack on the side Photo 2. Standard PC plug


This will allow your trigger circuit to actuate the flash directly. One end of the PC cord will be cut and its wires wrapped tightly around the appropriate ones from the trigger output cable. The solder joints will be covered with pieces of heat shrink tubing for electrical insulation.


Before you begin, gather the parts and tools below. You'll also need your trigger circuit or delay unit for testing.


3-ft of 2-conductor cable
PC cord
2-inch length heat shrink tubing (HST), 3/32-inch diameter

3-inch length heat shrink tubing (HST), 3/16-inch diameter

Helpful tools and supplies:
Wire stripper
15- or 30-watt soldering iron and solder
Wet sponge or towel
Lighter or matches to shrink HST


Preparing the PC cord


click for larger view  
  click for larger view

For PC kits, one end will already be cut as shown to the left. So basically, you're starting with half of a standard PC cord.


Using a pair of wire strippers, carefully strip back the cut end of the PC cord a distance of 1 inch. You'll see a copper sheath surrounding an insulated wire*. We'll call the latter the central wire. (This is the positive wire.) Pull back the sheath and twist the wires together as shown to the right. Then strip back the insulation on the central wire to within about 1/8 inch from the black jacket. It's important to make sure there are no stray wires from the copper sheath that touch the other wire.


Next, you'll need the gray 2-conductor cable. From one end of the cable, strip back the gray insulation about 2 inches. Then strip back the red and black insulation about 3/4 inch. The result is also shown to the right.


*Some PC cords will have a red wire and a black wire instead of a copper sheath. If so, treat the red wire as the central wire (positive) and the black wire as the sheath (negative.)


Splicing the wires

  click for larger view


click for larger view  


There are 2 sizes of HST, 3/32-inch diameter and 3/16-inch diameter. Cut the 3/32-inch piece into two equal lengths of 1 inch. Then slide them over the red and black insulation as shown to the left.


Next, twist the following pairs of wires tightly together as shown to the right: i) black wire and copper sheath ii) red wire and central wire.








Soldering the splices


click for larger view  


If you're new to soldering, see the Soldering Tips below. Then solder the splices. The result should look similar to the photo to the left. Again, make sure there are no stray wire strands that could bridge from one splice to the other.




    Soldering Tips

    • Solder in a well-lit, well-ventilated, open area. Avoid contact with all metal surfaces on the iron.

    • Keep the tip of the soldering iron clean by wiping it against a wet sponge or towel before and after each use. A clean tip should look shiny and silvery; any yellow or black material on the tip will get into the solder and may weaken your solder joint.

    • Once the tip of your soldering iron is clean, touch a bit of solder to the tip just before use. This is called tinning, and helps the solder run more evenly.

    • Heat the connection to be soldered by holding the soldering iron to it, until solder applied at the junction between the two melts and flows freely. This ensures the connection and the solder are both hot enough to yield a good solder joint. This should take no more than 10-15 seconds. After the connection is heated, try to get solder along the entire length of the connection by briskly moving the solder and iron along.

    • Avoid touching only the solder to the connection, and then the soldering iron to the solder to melt it onto the connection. The connection will be cooler than the melted solder and won’t form a good solder joint.

    • Let new solder joints cool for several seconds before examining them. There should be solder all the way around the connection, forming a rigid joint. When done, unplug your soldering iron and let it cool.

Shrinking the HST


click for larger view  


Slip each piece of 3/32-inch HST completely over the corresponding splice. Then, using a lighter or a match, move the flame smoothly back and forth along the entire length of the tubing, with the tip of the flame just beneath it. If you hold the flame too long in one spot or too closely to the tubing, you will notice smoke. If this happens, lower your flame and continue moving it back and forth. The tubing will visibly shrink, and will be acceptably tight-fitting after only 10-15 seconds of heating. See the results to the left.


Securing the splices

  click for larger view


click for larger view  

Slide the 3/16-inch HST over the gray 2-conductor cable so that it completely covers the two spliced wires as shown to the left. Then use a flame as before to shrink the tubing. The result is shown to the right.


The final, complete cable is shown below. Connect the red and black wires to the output of your trigger circuit and the PC plug to your flash unit. In the event that your flash unit isn't triggered through the cord, try reversing the connections of the red and black wires to your breadboard. This won't hurt your flash unit or the trigger circuit, but it will let you know if you have reversed polarity.


  click for larger view



Assembly instructions for other kits




About Tools Products Activities Galleries Projects Links Contact Facebook LinkedIn flickr
copyright © 1995-2020