Sending a trigger pulse by RF

Pimpom · 2010-12-25T09:46:54+00:00

I'd like to send a simple trigger pulse by RF at irregular intervals (seconds to minutes). No other data need be sent. No special requirement on the length or type of trigger signal. All that's needed is something like the momentary pressing of a light switch. The triggered device will be locally reset in between each triggered event.The transmission distance is roughly half a kilometer in unobstructed line-of-sight. I'm thinking of using some readymade transceiver modules, perhaps in the 2.4GHz band, so the RF portions are not really part of my question. My main concerns are -1. Delay between transmission and trigger output from the receiver should be less than 1 msec2. Avoiding false triggering by RF interference sources like vehicles, cellphones and other spurious sources.What approach do you suggest to satisfy the above requirements? For example, will a tone burst transmission and a tone decoder at the Rx be sufficient? Thanks in advance.

Dec 25, 2010 21 Replies

Rate this thread:

whit3rd 15 years ago

[about a remote RF timing signal]

If the remote is to be battery powered, it will go through a few phases; first, the carrier is established (during this phase, the receiver will have AGC fluctuations), then a signal is sent (something like a tone burst) and received (by a filter and trigger that rejects noise but not the signal). The AGC needs settling time, and the tone decoder will want a dozen or more cycles to detect (but can probably drop its output quickly when the signal is interrupted), so you'll actually get a 'receiver-end' time signal a bit AFTER hitting the button on the remote. Be prepared for this (and control that latency at all phases of the design).

Vote

Pimpom 15 years ago

The remote trigger source, along with other things, will probably be battery-powered (I haven't decided yet). But the battery will be a car battery, so there's no need to worry too much about conserving the charge.

I considered the AGC settling time and was thinking of making a continuous carrier transmission, with the trigger signal inserted at the proper time. Anyway, the tone burst method is just an idea. I'm open to suggestions. Perhaps a pulse train with the receiver accepting only a specified number of pulses within a given period??

Vote

Join the Discussion

Have something to add? Share your thoughts — no account required.

Didn't find your answer?

Ask the community — no account required