Eggtimer Tips and Tricks
Here's a collection of short ideas that may help you with your Eggtimer...
o Use a little piece of masking tape to hold the parts onto the board while you solder them. This is especially helpful with the little .1 uF bypass capacitors and the 1/8W resistors.
o You may find that the holes for the processor and the optoisolator chips are a little tight. We straighten the leads with a special tool before we ship them, but you may still find that a lead or two is slightly out of line. Use a jeweler's screwdriver or a round toothpick to gently guide any errant pins into the hole.
o A magnified light is really handy, as is some kind of stand to hold the board while you solder it.
o Don't oversolder the joints, just enough to cover the pad is all you need. There are some tight clearances on the board, so you are more likely to get a solder bridge if you go too gung-ho on the solder.
o Make sure that you check the orientation of the polarized components twice before soldering. In particular, the LEDs and the 10 uF capacitor are easy to put in backwards if you don't check carefully first. The "- - - -" stripe on the 10 uF capacitor must be facing AWAY from the processor chip.
o Conversely, you do not have to worry about the resistors, the small .1 uF capacitors, the resonator, or the pizo buzzer... they are not polarized.
o Use #4 nylon washers between the board with any metal screws that you use, we have found that one on the top of the board and two or three on the bottom (to act as spacers) works very well with #4-40 screws. If you have the room, use Nylock nuts too, they won't come loose in flight (which is a bad thing...)
o Nylon #4 screws work too, and they're very light. They also have the added advantage that in the event of a crash, they're going to shear and absorb the impact rather than passing it onto your Eggtimer board. Don't ask us how we know about this... :)
o We like using standard header pins to terminate the CHA and CHB outputs, and we wire-wrap 8" Quest Q2G2 leads directly to them. You can also wire-wrap #28 or #26 wire to them if you need to extend your igniter leads.
o If you prefer the "twist and tape" method of switching the power on, you can also terminate the SW terminals with header pins and wire-wrap some wires to them for this purpose. You simply have the wires hanging out of the payload bay somehow with about 1/2" of bare wire on each end, and you twist them together to turn on the Eggtimer. Once you get the "Ready" chirp, you tape them together and tape the loose ends to the side of the payload bay. Make sure it's secure, or your Eggtimer might lose power during a flight, which would be bad.
o That method is also applicable to the Reset terminals. With the Reset terminals, you need to break the connection to enable the Eggtimer. We have them hanging out of the side of the payload bay between the coupler and the booster, and we clip them off to start the flight sequence. Since they can't reconnect, you don't have to worry about the Eggtimer resetting in flight.
o JST or servo connectors work very well for hooking up the batteries. We recommend that you also tape them together with a wrap or two of masking tape, to keep them from coming loose in flight. (Another "learned lesson...")
o Instead of the "twist and tape" method on the power, you might want to use it on the Reset (RST) teminals and use JST connectors (with tape!) on the battery. It's backwards from the power... you twist them together to disable the Eggtimer, then separate them before flight and tape them up so they won't short.