Connect with us

Adjustable brightness torch??

Discussion in 'General Electronics Discussion' started by bikemech, Nov 20, 2014.

Scroll to continue with content
  1. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    Hi I have a request from a friend, he uses a torch with separate 12v battery power supply which he carrys a in his pocket, reason for separate battery is it lasts his whole work shift,
    He has asked me if it would be possible to fit a potentiometer ( dimmer as he put it) how easy would this be ?
     
  2. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Depends on the current draw of the torch.. it may be too high for a potentiometer to handle. The potentiometer will also waste some power... so it will not give him twice the battery life at half brightness.

    One other important question.. is the torch an incandescent or an LED?
    I would suggest he looks for an LED replacement... or we need to look into a 'PWM' method to 'dim' the light. This will save a lot more energy, and does not really 'need' to be adjustable with a dial if there are 1 or 2 preset dimmer values.

    Ideas, thoughts?
     
  3. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    Yeah good idea with the led, never thought of that, it's quite a high power torch , and the whole setup would need to be as compact as possible , will get some details about what he he is using now and get back, ideally looking for maximum brightness with around 6 hour life, battery can be changer so suite, as long as it's not too big
     
  4. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    PWM is the sensible option. Can be done fairly simply using a 555 driving a MOSFET. See http://www.reuk.co.uk/LED-Dimmer-Circuit.htm for an example. It is designed to vary the speed of a motor but there's little difference. Here's the circuit from that page:

    ne555-pwm-dimmer-circuit.gif
    Replace MOT1 with the torch (bulb or LED). D3 is not needed because the load is not inductive. Connect another 0.1 µF capacitor (ceramic) directly between pins 1 and 8 of the 555. That circuit should work pretty well. Can be built up on stripboard aka veroboard. Google stripboard construction for info.
     
  5. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    Think it's called breadboard over this side of the pond,
    But great Al have a look at that.

    Where is the controll on that diagram,
    Is it Q1?
    I understand 555 is IC?? And everything else ,
     
    Last edited: Nov 20, 2014
  6. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    No, a breadboard is a solderless prototyping system.


    Electronics-breadboard.jpg
    ^ Breadboard

    v Stripboard aka Veroboard

    FIFNQ72H1JUGO78.MEDIUM.jpg
     
  7. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    You just taught me something new :)
     
    KrisBlueNZ likes this.
  8. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Take a look at the yellow P1 on the left side of the diagram.
    Q1 is the FET that will do the heavy lifting switching the light on and off incredibly quickly (to make it look half-on)
     
  9. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    Google schematic symbols to find out what all the symbols are.
     
  10. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    C# = Capacitor
    D# = Diodes (D3 should be removed)
    P# = Potentiometer
    Q# = Transistor (Or FET.. Field Effect Transistor)
    R# = Resistor Values.

    555 = A very common IC used for .. You guessed it, timing applications, anything from signal generation (PWM) to momentary delays to hold circuits on, or hold them off.
     
    bikemech and KrisBlueNZ like this.
  11. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    Ahh damn, P1 , potentiometer 1 ?
     
  12. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Exactly!
    It's not a sprocket or chain.. so I guess you missed that ;)

    When you get some more details from/for your friend, we can help you move forward and learn/build this.
     
  13. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    Yeah I replyed before I read the last post , sorry guys :p
     
  14. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    Was that sarcasam I read in your text lol
     
    Arouse1973 and Frenoy Osburn like this.
  15. Owen Qin

    Owen Qin

    1
    0
    Nov 21, 2014
    :)
     
  16. bikemech

    bikemech

    456
    40
    Oct 23, 2014
    am i right in sayind D1 and D2 are zenna diodes?
     
  17. davenn

    davenn Moderator

    13,865
    1,956
    Sep 5, 2009

    Zener diodes, no, 1N4148 are just small signal switching diodes

    Dave
     
  18. bikemech

    bikemech

    456
    40
    Oct 23, 2014
  19. bikemech

    bikemech

    456
    40
    Oct 23, 2014
  20. bikemech

    bikemech

    456
    40
    Oct 23, 2014

    what caps are C1 and C2?
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-