Improved Control Interface

The following control interface board was developed to allow easy arming/disarming of a 2 altimeter system utilizing drogue and main deployment.  Utilizing this board, most of the hook-up can be completed and double-checked prior to final prep of the rocket.   Some altimeters such as the AltAcc support external LED's. The small traces are for mounting and connecting 2 such LED's.  The current carrying connectors are rated at 7 amp.

The CONNECT connector hooks up the LES charges.
The ARM connector serves as the power switch to the two altimeters.
The SHORTING connector shorts out each of the 4 LES charges.

During connection of the LES and during transportation of a prepped rocket, the SHORT connector should be in place and the CONNECT connector should be removed.

Clicking on the images below will bring up larger images suitable for photo-etching and labeling.

Parts Layout - top view

Note: The LES and altimeter connections are grouped by LES type, not by altimeter.  This method is less subject to human error.

M.G.  Chemicals' 600 series boards work well.  The following information is not explained completely in the instruction sheet.  (The board can be exposed with about 6-8 minutes of sunlight at noon on a clear day.  Exceeding this time is not generally advisable. The temperature of the developer should not be elevated.  Normal incandescent room light levels become a problem after about 20 minutes.   Subdued lighting is just fine when developing the board.  You'll need some light to see when the image appears so that the board can be removed from developer.   Avoid overdeveloping.  It causes the image to dissolve and fade away.  Development time should be around 1 - 1 1/2 minutes.  The developer will be good for many boards and can be re-used until it is very dark.)
I printed the image on a laser transparency.  Best results are obtained if the image is printed on the same transparency twice.  This darkens the image and prevents imperfections from allowing light to penetrate the black trace patterns when exposing the photo resist board.  Remember to put the printed side of the transparency against the circuit board.  (This makes a clean print and flips the image.   The image will turn back around when you put the components on the front side of the board and solder the traces on the back side.)

You will find that the small holes in the traces help center the drill bit and make drilling easy.  Use a 1/16" bit for the component holes.  A Dremel tool with a cutoff disk can be used to produce the hole for the DB9 female connector. (Mount the LED's against the circuit board and make certain that there is adequate clearance so that the DB9 case cannot short the traces or LED's during the vibration of flight.)

The hole shown in the large view of the parts layout allows wires to run through the front of the board to the back for the DB9.

Trace

It is desirable to melt solder onto the entire foil pattern to increase the current carrying capability of the board.  After all, the board will be used to melt wires in electric matches, not to carry small radio signals.

Lettering

Wiring Schematic

Parts List:

3 - 8 pin Radio Shack connectors (each slides apart to produce two 4 pin connectors)
1 - 3" x 6" type 600 photosensitized board (will accommodate 2 templates)
1 - bottle circuit board developer (M.G. Chemicals)
1 - bottle ferric chloride (M.G. Chemicals or Radio Shack)
1 - DB9 female panel mount connector (Radio Shack)
1 - DB9 male panel mount connector (Radio Shack)
1 - 8-pin miniature panel mounted connector (WMF-3912HRT mini-fit jr connector by Waldom/Molex)
1 - 4-pin miniature panel mounted connector (mini-fit jr connector Waldon/Molex)
optional:   2 - CLEAR red LED's  Radio Shack 276-307 (if compatible with altimeters)

Tools:

electric drill, 1/16" bit, 3/16" bit
glass picture frame to hold template against circuit board while it is being exposed
Dremel tool with cutoff disk
solder, soldering iron
plastic tray for development and etching, latex gloves