4 image::telemetrum-v2.0-th.jpg[width="5.5in"]
7 image::telemetrum-v1.1-thside.jpg[width="5.5in"]
9 TeleMetrum is a 1 inch by 2¾ inch circuit board. It was designed to
10 fit inside coupler for 29mm air-frame tubing, but using it in a tube that
11 small in diameter may require some creativity in mounting and wiring
12 to succeed! The presence of an accelerometer means TeleMetrum should
13 be aligned along the flight axis of the airframe, and by default the ¼
14 wave UHF wire antenna should be on the nose-cone end of the board. The
15 antenna wire is about 7 inches long, and wiring for a power switch and
16 the e-matches for apogee and main ejection charges depart from the
17 fin can end of the board, meaning an ideal “simple” avionics
18 bay for TeleMetrum should have at least 10 inches of interior length.
20 === TeleMetrum Screw Terminals
22 TeleMetrum has six screw terminals on the end of the board
23 opposite the telemetry antenna. Two are for the power
24 switch, and two each for the apogee and main igniter
25 circuits. Using the picture above and starting from the top,
26 the terminals are as follows:
28 [options="header",grid="all",cols="2,3,10"]
29 |=========================
30 |Terminal #|Terminal Name|Description
31 |1 |Switch Output |Switch connection to flight computer
32 |2 |Switch Input |Switch connection to positive battery terminal
33 |3 |Main + |Main pyro channel common connection to battery +
34 |4 |Main - |Main pyro channel connection to pyro circuit
35 |5 |Apogee + |Apogee pyro channel common connection to battery +
36 |6 |Apogee - |Apogee pyro channel connection to pyro circuit
37 |========================
39 === Using a Separate Pyro Battery with TeleMetrum
41 As described above, using an external pyro battery involves
42 connecting the negative battery terminal to the flight
43 computer ground, connecting the positive battery terminal to
44 one of the igniter leads and connecting the other igniter
45 lead to the per-channel pyro circuit connection.
47 To connect the negative battery terminal to the TeleMetrum
48 ground, insert a small piece of wire, 24 to 28 gauge
49 stranded, into the GND hole just above the screw terminal
50 strip and solder it in place.
52 Connecting the positive battery terminal to the pyro
53 charges must be done separate from TeleMetrum, by soldering
54 them together or using some other connector.
57 The other lead from each pyro charge is then inserted into
58 the appropriate per-pyro channel screw terminal (terminal 4 for the
59 Main charge, terminal 6 for the Apogee charge).
61 === Using an Active Switch with TeleMetrum
63 As explained above, an external active switch requires three
64 connections, one to the positive battery terminal, one to
65 the flight computer positive input and one to ground.
68 The positive battery terminal is available on screw terminal
69 2, the positive flight computer input is on terminal 1. To
70 hook a lead to ground, solder a piece of wire, 24 to 28
71 gauge stranded, to the GND hole just above terminal 1.