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Help with simple circuit; wireless torch

Discussion in 'General Electronics Discussion' started by jesbs1604, Feb 8, 2017.

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  1. jesbs1604

    jesbs1604

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    Feb 8, 2017
    So I am literally the newest of the new when it comes to these types of electronics. I know how basic circuits work but have never meddled with a circuit board or anything of the likes before. My knowledge is extremely limited so the answer could be relatively easy and I'm just not seeing it.

    Basically I've pulled apart a remote controlled helicopter and turned it into a remote controlled flashlight. All I did was replace one of the motors with the actual flashlights LED board and replace the tiny battery pack with the torches one. Now if I increase the throttle on the remote controller, the light turns on. This is almost exactly what I want except for one problem, it would make a lot more sense if the torch was perpetually in an on state but pushing the throttle actually turned it off.

    How would I go about switching the function of whatever part the motor played in the RC helicopter to be on unless triggered? For example if I didn't change the motor with the light, this would mean that the helicopter would have been always flying until you upped the throttle, then it would stop.

    So put simply instead of the throttle turning the light on, I want the light to already be on and have the throttle turn it off.
     
  2. TCSC47

    TCSC47

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    Mar 7, 2016
    With modern electronics of all sorts, things are not always what they seem. Something strange would seem to be happening with your circuitry. The only real way to figure out what is going on is to have a full knowledge of all your circuits and logically work your way through what is happening at each stage. That is an important lesson for commissioning any piece of equipment, or for fault finding. After many years an experienced engineer can take short cuts because they have seen a particular problem many times. But for the novice you have to break down things into their component parts or blocks.

    I would think your set up is too obscure for anybody here to give you an answer, but I remain to be proved wrong.
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    I agree with TCSC47. We will need at least a schematic of your setup to get the least idea what's going on.
    The throttle most probably controls the motor via pwm. That gives you the chance to reverse the trhottle function by simply placing an inverter between the rc receiver's output and the LED board. A 74HC14 or a simple transistor inverter (task 3) may do the job, depending on voltages and currents present in your circuit.
     
  4. jesbs1604

    jesbs1604

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    Feb 8, 2017
    Well I'll try and get diagrams later but if it is using pwm, how do I know? Also would putting a transistor inverter actually convert a low signal to a high signal? High to low I can understand but how does it make the light perpetually on if when the throttle is in it's "off" state it only gives a low signal?
     
  5. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    The definitive way is by observing the LED current with an oscilloscope.
    I guess that's out of your reach. Don't worry: pwm is THE way to control motor speed (hence LED brightness) in an efficient way. You can be almost 99.9 % sure it's done that way.
     
    jesbs1604 likes this.
  6. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    That's why it is called an inverter.
    Because apart from high -> low the inverter also changes low -> high.
     
  7. jesbs1604

    jesbs1604

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    Feb 8, 2017
    Okay well that's awesome!! I think I might start getting into electronics this is interesting stuff...
    So I have a few things like a capacitor, a transistor, some resistors. How do i make the simplest possible inverter? Do i need any more parts than I have and if so what would they be?

    I tried looking at task 3 but being a beginner I think I need everything to be a bit more straightforward.

    So I'm imagining that I'm shoving this thing right between the positive output from the RC circuit board, and the positive input for the LED board. That means that it's being given a constant low frequency and can be given a high one if I boost the throttle.

    Say I simply cut the wire between the RC board and the LED board, what parts should I put in between. Again keeping this as simple as possible! :p
     
  8. Harald Kapp

    Harald Kapp Moderator Moderator

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    Nov 17, 2011
    look at post #3, the last link. This really is a very simple circuit.
    Or look in our ressource here. The circuits described do invert the input signal. For this purpose they are basically the same as in my link.
    You may also want to study this tutorial which may be more appropriate to your level of knowledge.

    Impossible to say without knowing more detail like voltages and currents present as well as waveforms.
     
  9. TCSC47

    TCSC47

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    Mar 7, 2016
    If you are finding this electronics interesting and want to pursue it further, a use for an oscilloscope has already been mentioned. There are lots of 2nd hand ones for sale for less than £100 or so, and you don't need anything but a very basic one. Before that you would need a reasonably good multimeter £10, two power supply units £50?? and a signal generator. £50??. and you are prepared for anything! --- Almost!

    I haven't given any more details because you can find that on the web in much better detail than I could give here.
    Cheers
     
  10. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    After re-reading your first post I don't think that an inverter is going to solve your problem. If I understood that post you're saying that increasing the throttle turns on and continues brightening the LEDs but at some point any further throttle increase shuts them off. Is this correct?

    Chris
     
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