Hello everybody!
Thank you in advance for your time and patience.
Update:After following some advice you guys given me, and after having done some tests, I have accomplished to make it work in the desired manner. Big thanks to everybody
So I'm trying to create a simple circuit to control a 3w power LED's brightness,
and a brushless motor at the same time using a 4cell battery to power everything.
The idea is the more throttle on the transmitter, the more rpm - the more brightness.
The board I am using is Arduino pro micro.
I am using only 3 cells out of the 4cell battery, which is a 3000Mah 30C battery,
with a voltage of 11.8V total.
The Arduino will read a PWM signal from a receiver and with the use of a transistor,
current flow between the battery and the LED will be regulated.
In order to read the signal, I have tried two different things
Reading the iBus channel of my receiver
by just connecting it to the Rx pin of the board (pic 1)
The first circuit (picture 1) worked fine using a 3cell battery.
I was able to achieve exactly what I was trying,
but unfortunately once I changed to a 4cell battery and a different esc/motor,
I was getting no signal in any channel whatsoever.
Which really strikes me as odd.
In my second attempt (picture 2), I wired the esc to the receiver, and with a Y-cable,
I connected the Receiver 5v to the Board Vcc Receiver Ground to the Board GND Receiver Signal to board pin 6
Using a 3cell battery did the job, and I was able to read the signal.
When I've changed to a 4cell battery,
smoke came out (I think it was from the board)
And now the board doesn't work anymore at all.
Please feel free to ask anything in case my description of the problem is insufficient.
Can we please have a circuit diagram?
An image of a hand drawn schematic will be fine, include ALL power supplies, component names and pin labels.
Both the original circuit and the smoked one.
Copy and paste pictures are not very clear and you need to label the voltage supply Volts.
What is the transistor you are using?
You will need a current limit resistor in the transistors base circuit, currently you will be drawing more current from the output pin than it is designed for.
Thanks.. Tom..
PS. I'm off to bed, its 2:15am here in Australia...
May I suggest a 1K base resistor for the TIP120 and you remove the 33 Ohm resistor to "RAW". After all you are powering the whole thing already via your ESC connected to VCC.
@hmeijdam thank you for your reply
Both of your suggestions are of course correct.
As a matter of fact I was using the 1k resistor to the base of the TIP120.
I just forgot to include it on the schematic. So I've updated it now.
About the RAW pin in the 2nd picture, It really does seem unnecessary..
Do you believe that's the reason why the board burned out?
I suspect the very small voltage regulator has burned out. Ofcourse I do not know which board you have (your picture suggest a Promicro) and if so, what exact model and make of voltage regulator is on that board. The vast majority (or all) of Arduino's I own have a simple linear voltage regulator that turns the overvoltage 1:1 into heat. I would trust them to 12 volt, but only if I don't connect anything to the Arduino that needs some power. I would never trust them to 16 volt. And still then I had to replace a few of those voltage regulators over time.
@hmeijdam
The board I am using is indeed Arduino pro micro.
And what you suspected turned out to be true!
The board was not turning on neither by using the usb port, nor by the RAW pin
It could only be powered by using the VCC pin.
In order to make sure that the voltage regulator was burned,
I bridged the J1 pins, pugged in the usb and it worked like a charm.
I was also able to upload code so all good.
You're a lifesaver
Is it essential to replace the voltage regulator if I'm only going to power the arduino with 5V using the VCC pin?
And how safe is it to do so?
In the first circuit I have no clue why I'm not able to read the desired PWM signal using iBus with a 4cell 3000mah 30s battery,
whereas at the same time using a 3cell 800mah 70c works fine. Notethat I'm using 3/3 cells of the 3s battery, and 3/4 cells of the 4c battery. so it's the same voltage in the end. 11.8V
Does it have anything to do with capacity/discharge rate? I don't know.
The second circuit was also working fine using the 3c battery.
And I was able to read the signal.
It only burned when I connected a 4s battery
What I think I'm not getting is the idea of having a 12V line that powers the LED,
and at the same time power the board with a 5V line,
both of which have the same ground.
Is that how it's supposed to be?
Hi,
In the second you have gnd of the Rx connected to the controller, so you have a gnd reference for the controller to see the Rx output.
In the first you have no connection directly between Rx gnd and controller gnd, so no gnd reference of the Rx output at the controller, so it cannot detect the signal at the controller input.
Your observation is indeed correct.
What's odd is that in both cases, I get a correct signal using a 3s,
But using a 4s, I get no signal at all (first case)
Or the board is fried (second case)
But what I'll try to do with a new board that I'm expecting anytime soon, is
either connect receiver ground to board ground,
so the signal has a reference like you proposed -> in the first circuit
or remove the + 11.4V Battery - RAW connection -> in the second circuit
In that circuit, you should not feed anything to RAW, you are powering the Arduino with the 5 volt BEC output connected to Vcc.
Also, in the long run you will not be happy having placed an unbalanced load on the Lipo… the top cell will be less drained, perhaps it has only a slightly different load but it would be unquestioned if you used another step down regulator to get the voltage your lED needs, and feed that the full 4s votage.
Nicedrawings BTW, vastly preferable to the first "schematics".
Got it, thanks
And thank you for taking the time to answer as well.
Good idea about the DC/DC Step down.
Before I go ahead and buy one though, I have a final question:
The circuit on the drawings is part of a bigger one,
part of which are some more Leds that are also powered straight from the battery.
Since I'm removing the RAW connection, would it be "that bad" to just use all of the battery cells,
| no dc dc step down |
power all my LEDS with 15.2V - 16.8V (depending on battery charge),
and of course with the use right resistors?
If the leds are commanded by the same signal, I suggest you put as many leds in series as your voltage can drive. This would depend on the color of the leds., E.g. you can put more red leds in series than blue/white leds from the same voltage source as the forward voltage drop of the led increases when the wavelength of its color decreases.
No, and no extra rekulator is needed as you point out.
If you can efficiently use the voltage, as @hmeijdam suggests, or tolerate the additional waste of using the correct resistor.
Another consideration however is that your 4s 16.2 full charge voltage will discharge under load to, depending on how you treat your batts, as low as 12 volts…
I aim for a final recovery of cells to 3.7, which means in my circumstances about 3.2 under load. 12.8 volts.
That leaves capacity unused.
All components must be designed to operate properly at a wide range of voltages. In the case of a motor expected to deliver a certain power, this is normally handled by the ESC and feedback computed by, say, a flight controller.
I charge to 4.15 volts - that leaves capacity unused in any way.
That's why I have lipos that last a very longer time.
Please go to
and learn all you can about the chemistry you are playing with. Lipos are amazing sources of power, but must be treated with a good deal of respect and caution!
BTW if you can without it meaning that you would then have to kill is, tell is about what you are up to. Looks interesting.
This is also a correct observation.
And a fruitful discussion in general.
I think at this point I'm ready to combine all these information and try everything out anew.
I'm building a navigation lights - afterburner - retractable landing gear all-in-one arduino based system,
That is going to be installed in an RC EDF jet I'm working on
You can't use a resistor to regulate the voltage on the RAW input.
The voltage-drop on a resistor depends on the current.
dU = R * I
Voltagedrop = resistance * current
low current low voltage-drop
The Arduino pro micro is rated maximum 12V on the RAW-input
If you use a 4cell you feed in 14,8V regardless of the 33 Ohm resistor
Also before connecting the next arduino I would measure the "5V" from the ESC if it is really just 5V or if it is more if you connect a 4S 14,8V battery
Hey Stefan! So I wasn't really trying to regulate the voltage with the resistor, but the current just for safety.
And I was using 3/4 cells of the battery, so I measured the Voltage and it was 11.4V while I was experimenting.
The problem was that I connected both 11.4 to RAW and 5V to Vcc...
That's a good thought
And that's exactly what I did and worked out great!
Thank you for taking the time to answer
Nice. By all-in-one do you mean to say that includes the normal electronics on the aircraft? I know you are licking off a radio signal, but is there another processor for the rest? TBH I do not know how involved a flight controller in such a vehicle is, in quadcopters there's a serious bunch of processing on a fairly beefy processor. FC.
Good. I have always never used the ESC BEC, for no good reason other than a fear that something taking the ESC South, so to speak, might have implications for the BEC output.
So if I need 5 volts I can't get off the FC or PDB I use a small conservatively spec'd buck regulator and stick in there somewhere.
YMMV, like I say it is prolly just superstitious, always good to check votage before, well, you know.
(second case)