UHF Radio Telemetry System (Type UDF400)
Designed by Chapman Associates and manufactured in the U.K. by K-Tech Limited.
Overview
The UDF400 comprises a 16-key UHF Radio Command system that enables an operator to manipulate remote TV cameras and other electronic systems in situations where no command wiring is available. It can operate on any of the eleven channels in the 458MHz radio frequency band which the U.K. Radiocommunications Agency has allocated, and is licence-exempt when used in the U.K. since the CE approved transmitter and receiver modules have been built to, and are being used in compliance with, the R.A. Specification MPT 1329. A 433MHz version of the equipment is available to special order.
Main features
- The 16 keys on the transmitter normally comprise 8 momentary action and four pairs of electronically latched push buttons. In this standard configuration, the command system can provide, for example, Pan (Left/Right), Tilt (Up/Down), Focus (Near/Far) and Zoom (In/Out), using the eight (4 pairs) of keys with momentary action, and such functions as Lights (On/Off), Camera select (1/2), Transmitter (On/Off) and Power (On/Off), using the electronically latched push-buttons.
- Other, non-standard, combinations of the 16 keys can be provided to special order.
- All units use a very secure Family Identity code which is workshop re-programmable, together with a Unit Identity code (1, 2, 3 or 4) which can be set or altered by the user.
- Up to four receivers, all programmed with the same Family Identity code but different Unit Identities, can be independently controlled by the same transmitter.
- The small transmitter and receiver units (each is 146mm x 92mm x 45mm excluding switches, connectors and antenna) provide an operating range of up to 400 metres using the standard short (15cm) antennas attached directly to the units; this range can be increased significantly by the use of more efficient antennas.
- If required, the receiver can also be supplied as an assembled PCB for incorporation into customer’s own equipment.
- The telemetry receiver has a current drain of around 2.4mA (average) when using its battery economiser, or 24mA when operating continuously.
Telemetry Transmitter
| Power supply: | 6v (4 x 1.5v MN1500 batteries fitted internally). |
| Current drain: | less than 100mA in standby; around 37mA when transmitting. |
| RF power output: | 10mW (into 50W load) in the 458MHz (or 434MHz) band. |
| User controls: | (a) 16 legended push buttons, normally arranged to provide 8 momentary action and 4 pairs of inter-latching switches. (b) 4-way rotary switch to select desired receiver User ID. |
| Visible indicator: | A Red LED which illuminates when the transmitter is operating. |
| Connector: | SMB socket for attachment of antenna. |
| Channel change: | On four DIL switches, accessed by removing the blanking plug at the rear of the transmitter case. |
When any button is pressed, the transmitter starts to send the appropriate command signal. Since the receiver, when using battery economiser mode, ‘sleeps’ for 4 seconds and then ‘wakes’ for 0.4 seconds (this cycle repeating until a valid signal is received), the transmitter has been programmed to transmit for at least 4.5 seconds whenever a button is pressed to ensure that its signals will always be received. Only a brief press of any of the four pairs of latching buttons is needed in order for the appropriate command(s) to be actioned by the receiver.
The transmitter will also ‘hold-on’ for at least 4.5 seconds when any of the eight momentary action buttons is pressed, but the transmitted data changes to ‘null’ characters rather than active commands once the button is released. This is done to ensure that the receiver will always be ‘awake’ at some point during the transmission to respond to the command, whilst preventing overshoot of any push-button motor-controlled positioning functions.
Telemetry Receiver
The telemetry receiver can be supplied (a) ready-assembled into a robust case along with motor-control interface, switching circuitry and connectors to suit the new, K-Tech supplied, miniature CCTV pan/tilt/zoom unit OR (b) as a built and tested PCB module that can be interfaced and incorporated into a customer’s own system.Version ‘a’ - Ready-packaged Telemetry Receiver, with motor-control and switching interface
| Power supply: | 10 - 16v DC from an external source. |
| Current drain: (Control circuit) | The ‘Power-On’ relay and motor-control circuitry within the unit consume an additional 20mA when energised. |
| Input connectors: | SMB co-axial socket - for connection of antenna. 1.3mm barrel connector socket for D.C. power input. |
| Output connectors: | 25-way ‘D’ socket for switched outputs and motor control lines. 2.1mm barrel connector socket for switched D.C. power output. |
| Channel change: | On four DIL switches, accessed by removing the blanking plug in the underside of the plastic case. |
| Visible indicator: | A Green LED, which lights whenever the receiver is being powered. |
| Output switches: | FET switches (type FDV301N) to negative line, each able to switch a load of 220mA (continuous) or 500mA (pulsed). |
| Motor control: | 3 motor drive outputs, (Pan, Tilt and Zoom) each driven by a full bridge power driver IC. Each of the three outputs provides 9 volts, current limited to 40mA (to suit K-Tech camera system). |
| DC switching: | Relay switched DC (same voltage as input supply) to power TV camera(s) and other auxiliary equipment. |
| DC output capability: | Limited by the current-carrying capabilities of the internal ‘Power-On’ relay (2A maximum) and the inter-unit wiring. |
Version ‘b’ - Basic PCB module
| Module size: | 83mm x 70mm x 13mm. |
| Power supply: | 5 - 16v DC from an external source. |
| Antenna: | 2 PCB pads for antenna and ground connections. Choice of antenna is up to end-user. |
| Output connector: | 25-way ‘D’ socket for the 16 switched output lines. |
| Channel change: | On four DIL switches, accessed through a hole in the underside of the receiver PCB. |
| Visible indicator: | A Green LED on the receiver PCB which lights when the receiver is being powered. (This LED can be repositioned if required). |
| Output switches: | 16 x FET switches (type FDV301N) to negative line, each able to switch a load of 220mA (continuous) or 500mA (pulsed). |
The receiver can be operated either with a short wire antenna or, if greater range is required, a more efficient external antenna connected to the unit by low-loss coaxial cable.
On the basic PCB module version, 16 switched output lines are available.
When the battery economiser is in operation the receiver is switched on for only 400 milliseconds every 4 seconds and only 'locks-on' if a valid code is received. NOTE: A Valid Code is one that is sent by a transmitter programmed with the same two-digit Family Identity as that of the receiver AND switched to the same Unit Identity address as that which has been selected by the two DIL switches on the receiver PCB.
Once a valid transmission has been recognised by the receiver it will then stay ‘awake' for a further 10 seconds in case additional commands are to be sent. Any commands sent during this period can be of quite short duration since the receiver is already 'awake'. Ten seconds after receiving the last valid signal from the transmitter, the receiver reverts to the on/off pulsing cycle as described above.
If receiver battery power economy is not an important consideration, the economiser can be disabled by adding a shorting-link across pins LK1. The receiver will then operate continuously (drawing around 24mA), providing near-instantaneous responses to valid commands.
OPERATING FREQUENCY / DATA CODING
For the radio telemetry system to function, both transmitter and receiver must :-
(a) have been programmed with the same Family ID code (see below)
AND
(b) have the same frequency selected on their internal 4-way DIL switches
AND
(c) be set to the same Unit ID.
To change the operating frequency of a unit, locate the four small dual-in-line switches numbered 1, 2, 3 and 4. The switches can be found by turning the unit over, removing the blanking plug, then looking through the hole cut in the rear of its case.
