No re-design is not required. All one has to do is supply the alarm with it's own power supply, in this case the appropriate number of lithiums in series to provide adequate voltage to power the piezo. Herein lies the problem.
Typical primary (not rechargeable) Maganese Dioxide Lithium batteries put out relatively low current. But those which are considered "high current" will satisfy the demands of a typical piezo. A candidate would be a Sanyo PN 2CR5, but the size/weight may be an issue (mm: 34L x 17W x 45H @ 40g). THis unit is 2 cylindrical cells in series producing 6V with a max continuous discharge of 1.5A
Of course there are smaller hi-perf Lithium cells, but their O/P would have to be tested against the piezo being used (or get the current specs for the piezo).
Now the easy part. All that is required to modify your existing alarm is to remove the positive lead from the pigtail that goes to the RX. Now attach the Lithium pack to the alarm in such a way as to survive the crash. Attach the positive(+, red) lead to the positive terminal of the battery. Tap into the negative(-, black) going to the RX, and attach it to the negative side of the pack. Before you do this, buy a small switch and put it in that negative lead. The smaller the better, the idea being in a crash even the switch can be moved to the "off" position due to the impact.
That's it. Tha alarm will see the pulse width when the servo is on (singnal lead and GND), but will have it's own PWR supply if things go awry.
Chris Veitch wrote:
Guys
A number of vendors make these that plug into the RX and make a noise when the TX is off/out of range, I have one. Very useful if you land in very long grass on the slope in a reasonable manner.
Fortunately (touch wood) I have not had any problem landings at a distance for some time. In the days when I was learning or had some technical issue the landing out normally involved some amount of higher landing speed. This frequently leads to a movement of kit in the place which can disconnect components from the power source.
Therefore are there any vendors out there that can build one that would carry a lithium watch style battery as a power source and preferably be thin so that it would emit a noise if the TX was off or if it had no power from the RX. I think this would require electronic arming by switching the RX on and an off button on the unit.
Sounds like it could be a YNT project ??
Any takers ??
Regards
Chris
Chris Veitch
UK
-- *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~* Simon Van Leeuwen, Calgary, Alberta RADIUS SYSTEMS Cogito-Ergo-Zoom IAC25233*MAAC12835*IMAC1756*LSF5953*IMAA20209 *~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*~*
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