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Jan 03, 2015, 04:12 AM
Synthezisers and RC :-)
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Mini-HowTo

Low voltage alarm on MultiWii SE v2.5


OBS! This is only if you fly 3s LiPo! You can damage the flight controller if you try this with 4s battery!

Here are a how-to for installing low voltage buzzer alarm on the MultiWii 2.5 SE.
You need to know how to solder.
If you think you can do it, thats fine. If you hesitate, don't do it.
Perhaps you have a friend that can solder who can help or use a separate low voltage buzzer and connect it to the balance of the battery.
Installed and tested on MultiWii 2.2 sketch.
Now is a good time to make a backup of your PID.

OK, lets start soldering.

You need some wire and resistors. One 33K Ohm, one 12K Ohm and one 39K Ohm or a 51K Ohm(instead of 12K and 39K). See PIC1
I only have 12K Ohm and 39K Ohm resistors so i used those instead for a 51K Ohm, i just soldered those in series.
I make this guide with resistors 12K Ohm and 39K Ohm.
If you have 51K Ohm thats ok.
A soldering iron with a nice sharp tip, good quality solder and some heat shrink tubing and a voltmeter.If you don't have one, consider to buy one. They are a great tool.
You can built it your way just check PIC14 for schematic.


1, Solder the resistors 12K and 39K together.See PIC2

2, Solder one wire to positive (+) and another wire to negative (-) on the power distribution board. See PIC3

3, Solder the 33K resistor to the wire that goes to negative (-) on the power distribution board.
Then solder 12K and 39K (or 51K) to the wire that goes to positive (+) on the power distribution board.
Apply some heat shrink over resistors and wire. See PIC4

4, Apply even more heat shrink so that it covers the resisitors.
Solder the end of the 33K and the end of 12K + 39K (or 51K) resitors together.See PIC5

5, Now to the tricky part! Look for A3 connection pad on the MultiWii. A3 is voltage monitoring input. See PIC6
Apply little solder to A3 pad and then solder a wire to it. See PIC7

6, Take the wire from A3 pad and turn it a couple of times around the standoff next to it to secure it. Put some CA glue over it to secure it even more.

7, Take the wire and solder it to the junction of resistors(33K--o--12K+39K). See PIC8

8, Apply some more heat shrink tubing to isolate resistors and wire. See PIC9
I glued the heat shrink packet to the frame with CA glue.

9, Propellers off!! Check that everything are ok, if it's ok then connect power to the system. NO!! blue magic smoke. Everything OK. ! See PIC10

10, Connect MultiWi to your PC with the FTDI and run Arduino on your PC. Open the config.h tab in multiwii.ino sketch and uncomment #define BUZZER and #define VBAT, you also need to make your other settings for your aircraft in the sketch. Do not forget that!.
This next step are not a must, just do it if the voltage reading are way off. Go Here for calculating VBATSCALE(V BAT monitoring: - on the website).Mark the box "Check to enable Battery monitoring" and click "Open V-BatCalculator". Now you need your voltmeter. The calculator tells you what to do. Type in your numbers in the sketch. Now upload your sketch to MultiWii.

11, The buzzer i use are from Armattan, TMB12A05. Before you can connect that buzzer to MultiWii you need to cut the connector for buzzer in two parts and also apply some heat shrink tubing over them. See PIC11

12, Connect buzzer to MultiWii.The positve (red) connector to PIN D8 and negative(black) to any free ground(-) PIN. D8 is the default buzzer PIN, no need to set it in sketch.See PIC12

13, Now you should have a voltage reading in the GUI.See PIC13

14, Finished, Go and fly with a buzzer.

Read the MultiWii sketch, you find a lot of information there.
I added a pic. of the stick configuration for MultiWii 2.2. Mode 2

P.S The Armattan V-Tail 355.
It fly so beautiful with the MultiWii.
Last edited by JoacimW; May 28, 2015 at 09:09 PM. Reason: Updated
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