Indipendent LMA

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solved

[Mr.RC-CAM]

You can power the LOMA from a dedicated battery. The change is simple: Connect it's power and ground to the new power source. R/C Sig and ground would go to the Rx. It would be a good idea to place a 1K resistor in series with the R/C sig pin of the PIC too.

As for a battery, you want something that has as much mAH as possible and a voltage curve that supports the device's 5V operation. Perhaps four AAA NiMH cells. Lower voltage can be used, but the loudness will suffer.

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Do I really need the 5V...

[Mr.RC-CAM]

General comments ...

... the PIC will run Ok using everything above 2V...I don't believe the PIC's internal OSC's accuracy will work in your favor at such low voltages. They are calibrated at 5V. If you are custom writing your PIC code then you can work around that. But, the existing LoMA firmware is based on normal BEC powered apps (but is tolerant if the voltage varies a bit). A LoMA operating on 3.6V may be OK, but you will have to test it out.

...are also buzzers that works from one to 5 V.The audio level is related to operating voltage. Low voltage will substantially reduce loudness of a typical audio alerting device. Try out the candidate at low voltage to see if you like what you hear.

[Acetronics]

:) Hi, Daan

Have a look to PIC xxLFxxx datasheets ...it's the extended supply range and specs are guaranteed from 2 to 5.5 v ...

normal series are guaranteed from 3 v ...

Alain

PS : for buzzers, I use a MAX 732 or 733 to raise voltage to 12 or 15 v :eek: ... but others very small converters exist for 5 v output, just play with the Enable Input !!!

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Raising the voltage, I would like to have power so that I have 24 hours of beeping... good idea, nobody knows the perfect cells to use for this project

[Mr.RC-CAM]

...nobody knows the perfect cells to use for this project"Perfect" for you might not be perfect for someone else. Designing something like this is all about compromise (size vs. weight vs. mAH vs. cost ... ). Just search the catalogs and find what is best for your requirements.

Here is a typical exercise. LoMA consumes 80mAH in one day. The battery must provide useful voltages during this period (4.5V to 5.5V is nominal). Here are four of possibly hundreds of solutions:

Example 1, Low weight:
Two Energizer 2L76 in series with one 1N4148 silicon diode (for hot voltage drop to 5.5VDC). Estimated weight ~7 grams, alarm duration one day continuous. However, 100uF cap across battery may be required for good performance (which would affect weight).

Example 2, Longer alarm duration:
Two Energizer CR2450 in series with one 1N4148 silicon diode. Weight under 15 grams. Estimated continuous alarm duration of 4 days.

Example 3, Single Cell, long duration:
One Energizer EL223in series with one 1N4148 silicon diode. Estimated weight 37 grams, continuous alarm duration of 10 days.

Example 4, Rechargeable NiMH:
Four Energizer NH12 in series. Total estimated weight 50 grams, alarm duration 18 days continuous.

The list goes on and on. Each choice has its hits and misses. You have to decide what is most important and possibly accept a compromise solution. That is the nature of the engineering beast. And as mentioned, you can use a DC-DC boost Vreg to manage the voltage from a single cell. That adds complexity and possibly other issues. Just another branch of the compromises.

[ZAGNUT]

cheapest and lightest batteries would probably be the 3 volt lithium CR2032, put in series for more volts or parallel for more duration. should cost around one euro for a pair at most camera/computer shops.

and if you really want it to be independent then don't tie it to the receiver, just set it up to go off after a certain amount of time. maybe use a small jumper to disable/turn it off. this way it can all be contained in a single small package that should survive any crash and still work.


dave

[Acetronics]

Hi, Uit

You should make a search around the MAX 630 ... I remember an application in conjunction with a MAX 8212 called " The ultimate way to sqeeze a 9 v Battery "

Title explains itself ...

Alain

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thx