Rescue helicopter micro with 1S batteries

I bought at Banggood Lost Plane Finder Alarm RC Helicopter Tracer (SKU061509) www.banggood.com/buy/Sku061509.html . I wanted installed on airplanes and gliders. But having made a crash in the tall grass with a NEW V120D02S it would be very useful to equip it. But these alarms work from 4 to 6V. On the V120D02S it does not work because the battery is 1S (3.7V). Anyone have an idea to run this alarm, or another system, which is integrated on a V120D02S.
Thank you.

You can run a step-up converter that will step 1-4v up to 5V. They sell them i.e. on ebay.

I hope it's not very big, because it still adds weight to this little chopper. On finder alarm, there is a connector to go to the RX and another por go to the servo. The negative is common to the two connectors but the positive and the order have an input and an exit. What I fear with the converter is to grill the servo, and may be the RX, what do you think?

Absolutely it will!

What you'll have to do is branch off the power leads from the battery, the factory parts will all still receive 4.2V directly from the 1S pack and the step-up converter will only boost voltage to the alarm...

Here's the issue with this idea tho- Boost converters are HORRIBLE INEFFICIENT. They draw two times the power from the battery as they output (if it's putting out 1A it's, very literally, drawing 2A from the input) I wouldnt do it if I were you man, I'd just fly my tiny micro 120 copter closer so you dont loose it. Add the extra weight of the equipment (the alarm, the boost converter and the wiring) with the extra load and it's going to shorten flight times VERY significantly

It is true that the idea of the converter is fine provided that it does not consume too much power and not too weighed down the mini chopper. But I was thinking more of a Deviation programming to generate the functioning of a buzzer. For example make config on a channel (Aile, Rudder or Elev ) would activate a servo position outside of its operating range, and then generate an alarm buzzer in the chopper. I thought of a microswitch, but if we can be avoided because it would be less reliable. With telemetry also has the info "voltage and temperature", but I think it would be more difficult to achieve.
What do you think?

I think, than in a micro "high-end-toy" grade heli such as the 120 that it's probably impossible. The issue is the integrated (and non seperatable) FC and receiver board all-in-one.

Doing what you describe would be no issue at all for a real radio system. That or write a new FW for the 120...

In my opinion (if it were mine) I would simply not fly it where it might get lost and if I really insisted I'd stick a couple LED's (maybe make some flashing) on it and call it good. The boost converter is, once again, very very inefficient. The weight is ok, the big issue (in my mind) is the boost converter's added draw. How many mAh is the batteries you use?

The idea of ​​LED is also very good, but once the chopper in the grass, it would be much less effective than a buzzer. My batteries are 600mAh. The fact of flying above the high grass is also interesting because in case of crash, there is a lot less damage.
In fact you should have an extra channel operate from the TX with a buzzer provided if the radio link works!
What do you think as a timed system that would switch after 10 minutes (after the normal flight time is 6 to 8 minutes) and that would beep every 30 seconds for example? But where to find it?

To me, looking for an off-the-shelf system is the wrong way to go about this. The idea of a timed system is a good one and it would only be MAYBE 70-100 lines of super simple code on $3 worth of parts (an ATTINY, a buzzer and a few passive components).

Sorry but I do not understand "70-100 lines of super simple code" is it a program? and "an ATTINY" what?

In fact it has to run under 1S batterie (from 3.5 to 4.2 volts) it starts to make a series of 3 beeps 0.5s, space 1s (0.5s, 1s, 0.5s, 1s, 0.5s) from 10 minutes and every 30 seconds.

You'll also need to deal with the servo connectors. The Rx in the V120D02S uses micro connectors, whereas this has standard servo connectors on it. Soldering on new ones is probably the better solution, as you're going to be adding enough weight as it is.

What CK is suggesting is getting a microcontroller, connecting it in line with one of the servos, then adding a buzzer and LED. You'd have to write code to read the PWM signals on the servo line (for some reason, there isn't a library for that) and write them back out, then if the value doesn't change in however many minutes, set of the buzzer and LED. Pretty trivial, except for reading PWM values. And that's not hard since you just want one.

He's right that there's probably only $3 worth of parts in it - if you have them in your parts bin. If you were to buy them in onesies just for this project, it'd be much harder to hit that price point.

I understand pretty much what you say, but unfortunately I can not do it all!

Hi.

You could try replacing stock Esc with Blheli firmware based esc. If I remember correctly when left on ie no throttle movement. Esc After set time makes motor beep. Worth looking into

Can't you just hit the throttle occasionally and see where the grass twitches?

Replace the music of the ESC and switch on throttle is not significant when there is wind in the tall grass and surrounding noise. When I crashed my V120D02S I tried to do it, but without result. I think the best thing about this type of helicopter is the buzzer. Nevertheless thank you for your ideas.
I am waiting for further information because the challenge is to find the components in 3 to 5V.

Just look for "3V boost converter" at your favorite electronics site. I found this:
www.aliexpress.com/item/1Pcs-XL6009-DC-D...dule/2048353079.html

Thank you for your research, but the circuit you give me is too big, what a pity because the standby current was interesting. What do you think of this www.aliexpress.com/item/2-pieces-lot-min...tep/32268732761.html ? But I do not know his standby current.
So I would insert it between the servo and the lost plane buzzer. The V120D02S servos run from 3 to 4.5V. Do you think more than 0.5V will damage them ?

Yes, the lost plane locator has to go between the Rx and the servo. It watches the servo line so it can go off if there's no activity.

Hard to say whether 5V will damage the servo or not. Why risk it? Just insert a resister in series with the servo after the locator to drop the voltage back down.

Resistor is not the way to go there. The voltage drop of the resistor will change with the load, and with a servo, the load changes drastically. If anything, using two diodes with a 0.7v drop could be used, but either is not a clean way to handle it. Why not keep powering the servo from battery and only attach the signal line?

Here is the installation I wanted to do because of 1 of the 3 plane lost locator the V + was welded on 2 different locations (see items 2 and 5), as I do not know how this circuit works, I wanted to do the same again. In fact the inputs and outputs V + (2 and 5) are welded together, as indeed V- (3 and 6). So it simplifies everything. The first scheme is red dashed line, the final red solid lines.
Which channel should I put it?
Thank you for your help.
saidem