DIY cheap and easy remote controlled lightning - LED driver

[mnwizard]

Originally Posted by CyprusDave

BTY, I don't know if anyone else will agree, but I vote this as sticky material

+1

[sutty]

No, not sticky, unless it gets stuck right! If it gets stuck, page one will get smaller again.

Until we can get the two at the top put in the super stickie, and this one with it, then I say no.

If Bugster reads this and can do that, then without a doubt, a big +1 for a stickie.

At the moment, I only think the super stickie, and HeliPort, deserve to be on page one. Don't know if others agree.

Cheers

Sut

[Jonnyheli]

I think we need another moderator from this section. Makes sense to have a user moderating the section that they always post in. I vote Jonny as a second moderator for the Belt CP section. I'm regularly on here and would sticky all of Raf's posts in the super sticky thread, providing I had the powers:glasses2:

+1 though.

Dave and Raf, your both clever. Can you make a chip that can be inserted into my brain, which has everything on it I need to know about electronics?

Jonny

[jperkosk]

+1 for sticky and for ordering the stickies right, Bugster, where RU??? Raf has already asked for that
+1 for Jonny The Moderator
-1 for Jonny's chip implant: sorry, you'll have to do it the old-fashioned way, them brain chip implants are dangerous, haven't you seen MI3?

[redbird300]

Andrew, these vids are for you buddy !

About your question concerning the two orange LEDs not being in sync:

I quickly made a few circuits on my faithful prototype circuit board, don't mind the actual form, it could be made very small if needed on a real circuit plate, just showing what can be done in a short time.

The first is a circuit where two LEDs will flash in perfect sync:

YouTube

YouTube

And if you want the LEDs to alternate, still staying in sync of course, here's a second one:

YouTube

YouTube

And here are the diagrams, they are dead easy to build, and the circuits could be incorporated in the LED driver, simply connect the + and ground of these circuits to the wires on the LED driver where we now have the LED and series resistor.

-) The 4093 integrated circuit costs only around 0.25 euro, it's known as a "four fold 2-input NAND Schmitt trigger".
-) You need two LEDs in parallel in the first diagram, there is only one in this drawing. Resistor R2 is only needed once though.
-) Power supply is marked "9 Volts", but it also works with 5 to 6 Volts, just take smaller values for the series resistors with the LEDs, or they won't shine very bright. for example 500-600 ohm on 5 Volt.
-) Smaller values for R1 and C1 will make for faster blinking, there is a linear relationship between both these values and the frequency. You could for example use half of the actual values, and the LEDs would blink twice as fast.
-) Oh, and "rood" is simply Dutch for "red"

[sutty]

I was only posing the question Raf, you didn't have to go and do it! That having been said, you are the man, how cool is that, I think that will look much better than them coming slowly in and out of sync. Don't know which is best really, but I think I quite like the ones out of phase.

That prototype board looks cool. I could do with one of those to test my little circuit, but since it might be the only one I ever do, perhaps it would be a little over the top?. Oh, and by the way, thank you so much for all the help. As for me paying too much, if the bits I managed to find are actually right, well I say "stuff it", I'm gonna go for it, as it was way too hard to find them in the first place, and the order is prepared, and finding the alternatives might just confuse me even more, lol.

And for anyone else wondering what I am talking about, I will post when I'm done with a little tiny build thread of the project I'm up to. Not very exciting, but it is a wee bit electronical, and I haven't done anything like this for years, so it might/should be fun.

It's secret for now, because if it all goes belly up, I'll probably just keep it to myself and go and hide in a dark corner.

Cheers

Sut

[jperkosk]

Brilliant, Raf, never would've thought of using NAND gates as an oscillator!

Sut, on the second diagram the D1 & D2 blink in the opposite phase, meaning while D1 is on D2 is off and vice-versa, gives you another blinking option!

Edit: should've watched videos before writing this response , but wasn't there only the first one at first?

[redbird300]

Originally Posted by jperkosk

.. but wasn't there only the first one at first?

Don't worry Jerry, I ask myself that exact same question every time when I look at my helis....

[jperkosk]

LOL, so true. So many times I kept making a mental note not to leave them together locked up in one room after dark, then one lapse of memory and BANG! there is new one sitting on the shelf in the morning

[Jonnyheli]

Raf, that's really cool, I wish I could do stuff like that. Oh well, plenty of time to learn

Do youthink you could make something like this? I would like to think this is real, but some of it looks a bit like stop frame animation.

YouTube

YouTube

Jonny

[sutty]

I think that looks real Jonny.

[redbird300]

Indeed, that's real, you can get automation Lego kits, with programmable hardware. When I was a teenager, I did things like that myself, using the parallel port of a computer, adding hardware to control stepper motors, and write software to control the 8 bits on the port. A bit like a primitive DIY plotter. Managed to make it work, converting AutoCad files and so on, but the mechanical precision and speed was terrible. Learned a lot from it though.

[redbird300]

Now this is a nice one, if I’m allowed to say so myself, stay with me here !

As I said before, if you hook up the LED driver to a proportional channel (not a switch, but a knob or slider, like the AUX8 channel on a DX8), you can change the brightness of the LEDS from minimal (completely dimmed) to maximal during a flight. But you can only change all the LEDs together. Wouldn’t it be nice if that single knob would allow you to switch on more and more LEDs in the heli, the more you turn it ? After all, we don’t have 20 channel transmitters to control all LEDs individually with separate LED drivers, and we need to work with what’s available.

By carefully positioning the LEDs over the whole of the fuselage, you could make for a nice effect. For example, first the warning beacons, after that some headlights, after that the tail light, and so on.

Well, the principle was not that hard to figure out: we already have a varying voltage at the output of the LED driver, which could be used to drive a bargraph like sequence of LEDs, a bit like the VU meter in your sound system at home. And all this with a single chip and 2 resistors ! I hooked up 10 LEDs in a prototype, and did the test. You could hook up more LEDs with an extra chip, BTW.

There’s a demo vid: the power supply at the right delivers the fixed voltage for the circuit to work, it represents the main pack of the heli, or whatever voltage is available, like an RX pack for example. The prototype board in the middle represents the circuit that can be hooked up to the previous made LED driver. And the digital power supply at the left represents the changing voltage from the RX, as you turn the knob on the choosen channel. I start with zero volts, no LEDs will light up. When slowly changing the voltage to 5.6 Volt you’ll notice more and more LEDs activating, one LED about every 0.5 Volt increase. The resistors are calculated in such a way that all LEDs are active at exactly the maximum output voltage of my LED driver - BEC, 5.6 Volts in this case.

Here’s the vid, going from zero to 5.6 Volts and back to zero, watch the LEDs meanwhile:

YouTube

YouTube

And the circuit diagram, using a cheap LM3914 integrated circuit, they don’t come much easier:

[redbird300]

Oh, and I case if anyone would wonder if I run to my local electronics shop each time I build something new. Well, I don't, it's just like helis, you keep the most common spare parts at hand, lol. Difference is that I'm way longer into electronics than helis, so admit that this isn't exaggerated. Had to clean up my workroom lately, said the missis, that could also explain it.

[redbird300]

One more thing:

A small change in the same circuit allows you to activate just a single LED of your choice (or group of LEDs, as you could connect some in parallel), instead of more and more LEDs as you turn the channel knob, as shown before. Still using only a single (proportional) TX channel.

You could for example imagine three groups of LEDs in the heli, like beacon lights – searchlights - normal lights. By turning the channel knob, one of these groups would become active. When turning the knob some more, a next group would become active, and so on. You need to disconnect pin 3 from pin 9 in the above diagram, but keep pin 3 of the integrated circuit connected to the main power supply, done.

There are many possibilities, it’s up to the creativity of the user. A little vid again, not with 3 but with the 10 LEDs that I used before, enjoy:

YouTube

YouTube

[redbird300]

And in case anyone is interested to know more, here's the datasheet of the LM3914 integrated circuit, with some practical examples in it.

[sutty]

Thanks Raf, I downloaded that and had a look. Very interesting. I'm getting a little scared now though. I'm pretty sure I don't need or want another hobby.

Cheers

Sut

[mnwizard]

Originally Posted by sutty

Thanks Raf, I downloaded that and had a look. Very interesting. I'm getting a little scared now though. I'm pretty sure I don't need or want another hobby.

Cheers

Sut

+1 Sut..... (Wiz has run screaming from the room)

[badfrog]

Originally Posted by redbird300

Well, I decided to start a new thread about this subject, some scale flyers might be interested.

Here is the first post from another thread, and I'll continue the story below this quote:

I started working on a more final version of a remote controlled LED driver now. It will be used it in a scale project later on.

Below are some pics, look at them first, but come back to read these notes also:

1) The whole thing will be put in a very large piece of shrink wrap (not the LED contacts of course), but I wanted to show the pics before I did that.

2) I used the circuit board of a larger servo this time, a broken Spektrum DS821, to allow for more current, thus more LEDs. Still need to find out how much the circuit will take continuously before it starts heating up, but the LEDs take only 10 mA a piece, so that should allow for a whole lot of LEDs.

3) The black and orange wire that you see in the pic showing the back of the circuit board, are the wires that went to the servo motor. Well, I used thicker wire, but that’s where the motor was connected. They bring + and - V to the two contact strips.

4) The 5 kilo-ohm potmeter from the original servo has been replaced by 2 fixed resistors (2.2 and 4.7 kilo-ohm), look at the left side of the board, you really need a soldering iron with a very fine, needle like tip !

5) The little project has a connector strip at the right side with 2 x 8 connector pins, to allow for 8 LEDs to be separately connected. The normal servo connectors fit, these have the standard 1/10 inch spacing.

6) Last picture: I removed the useless signal wire from the servo connector going to the LED, and did cut the unneeded part of the connector. This will allow the nut and washer around the chrome LED housing to be removed (over the servo connector which is too wide otherwise) when I will need to mount the holder in a fuselage. There are also black plastic holders available.

7) You’ll need a resistor in series with the LED to limit the current, most LEDs take around 10 mA. Some might take a bit more. My resistor is under the black shrink wrap close to the LED, barely noticable. You need to calculate the value of that resistor, depending on the specs of your LED and the output voltage of your BEC. If you would use all the exact same LEDs, you could get away with a single resistor for all LEDs, soldered between the board and the contact strip. Mind the dissipation of the resistor if you do that.

8) Connect the board to any free channel of your RX, and assign a switch to that channel in the TX. No external power supply needed, you’re basically done. Flipping the switch will activate/deactivate the LEDs.

9) You also need to set “travel range” of that channel to maximum, 150% in my case (Spektrum TX/RX), otherwise you won’t get the full voltage from the BEC to the LEDs. This is also a handy way to dim the LEDs, if you would find that they give too much light (with the chosen resistors). An example: with a 5.6 Volt BEC, and travel range at 100%, I got only 3.1 Volts going to the LEDs, but at 150% travel range, this was the full 5.6 Volt. In fact, 3.1 Volts is enough for the LEDs, but I don’t like the idea that I can blow the LEDs up by changing a setting of the TX. So use the full 150% setting, and add resistors as needed, you’ll need to do that anyway in most cases. And it allows for a better spread on the brightness of the LEDs, see below for that.

10) If you have a free proportional channel on your TX/RX, like the AUX3 channel on a DX8/AR8000 combo, you can change the brightness while flying, by turning the AUX3 knob on the TX. Depending on how you connected the two unequal resistors that replace the potmeter, you’ll have control over the LEDs on the low or high half of the channel. The other half won’t change a thing, they will stay in the last position. Not important, but nice to know. Just change the order of the resistors if you regret how it works after having build the project.

11) Use super bright LEDs, you won’t believe how much light these produce nowadays.

12) Dimension are about 5 x 2 centimeter, but as you can see, it could be made a little smaller even, by soldering the resistors straight up, cutting the bottom circuit board, using a separate connector system, etc... Not that important in my particular case, and I preferred mechanical and electrical stability above miniaturization. The weight is 10.2 grams, connector cable included to the RX, but without the LEDs.

In short: I just connect this board to the RX and connect the LEDs to the board.

Tested on the bench in one of my helis, works like a charm. Enjoy.

very cool! I never thought about "re-purposing" busted cheap servos...I just dug out the 2 gear stripped SG90's from my trash!

SO...
I need to unsolder the motor and the pot... the motor wires are the power feed, the resistors go across the red and black on the pot? where do you buy the led's and what are the specs and resistor combo I need?

[redbird300]

Originally Posted by badfrog

I need to unsolder the motor and the pot... the motor wires are the power feed, the resistors go across the red and black on the pot? where do you buy the led's and what are the specs and resistor combo I need?

The motor wires are used to connect the LEDs indeed, and the resistor combo is soldered to the 3 wires of the (removed) pot.

Look at the inscription on the pot, or measure the value, and you need at least as much in total with the 2 resistors (they are connected in series), look also at point 4).

You can buy LEDs in any electronics store, or desolder some from used equipment. Normally they work on 2 to 3 Volts, that's why you'll need a resistor in series with them to limit the current to something like 10 milli-amps, or you might blow them up.

Hope this helps.