3 image::telemetrum-v1.1-thside.jpg[width="5.5in"]
5 TeleMetrum is a 1 inch by 2¾ inch circuit board. It was designed to
6 fit inside coupler for 29mm air-frame tubing, but using it in a tube that
7 small in diameter may require some creativity in mounting and wiring
8 to succeed! The presence of an accelerometer means TeleMetrum should
9 be aligned along the flight axis of the airframe, and by default the ¼
10 wave UHF wire antenna should be on the nose-cone end of the board. The
11 antenna wire is about 7 inches long, and wiring for a power switch and
12 the e-matches for apogee and main ejection charges depart from the
13 fin can end of the board, meaning an ideal “simple” avionics
14 bay for TeleMetrum should have at least 10 inches of interior length.
16 === TeleMetrum Screw Terminals
18 TeleMetrum has six screw terminals on the end of the board
19 opposite the telemetry antenna. Two are for the power
20 switch, and two each for the apogee and main igniter
21 circuits. Using the picture above and starting from the top,
22 the terminals are as follows:
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25 |=========================
26 |Terminal #|Terminal Name|Description
27 |1 |Switch Output |Switch connection to flight computer
28 |2 |Switch Input |Switch connection to positive battery terminal
29 |3 |Main + |Main pyro channel common connection to battery +
30 |4 |Main - |Main pyro channel connection to pyro circuit
31 |5 |Apogee + |Apogee pyro channel common connection to battery +
32 |6 |Apogee - |Apogee pyro channel connection to pyro circuit
33 |========================
35 === Using a Separate Pyro Battery with TeleMetrum
37 As described above, using an external pyro battery involves
38 connecting the negative battery terminal to the flight
39 computer ground, connecting the positive battery terminal to
40 one of the igniter leads and connecting the other igniter
41 lead to the per-channel pyro circuit connection.
43 To connect the negative battery terminal to the TeleMetrum
44 ground, insert a small piece of wire, 24 to 28 gauge
45 stranded, into the GND hole just above the screw terminal
46 strip and solder it in place.
48 Connecting the positive battery terminal to the pyro
49 charges must be done separate from TeleMetrum, by soldering
50 them together or using some other connector.
53 The other lead from each pyro charge is then inserted into
54 the appropriate per-pyro channel screw terminal (terminal 4 for the
55 Main charge, terminal 6 for the Apogee charge).
57 === Using an Active Switch with TeleMetrum
59 As explained above, an external active switch requires three
60 connections, one to the positive battery terminal, one to
61 the flight computer positive input and one to ground.
64 The positive battery terminal is available on screw terminal
65 2, the positive flight computer input is on terminal 1. To
66 hook a lead to ground, solder a piece of wire, 24 to 28
67 gauge stranded, to the GND hole just above terminal 1.