Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1]   Go Down

Author Topic: voltage reducer  (Read 1530 times)

tubby tomo

  • Guest
voltage reducer
« on: April 07, 2008, 08:51:30 PM »

hi to you all could a clever chap tell me what parts i would have to get from maplins to build a power reducer i have20 light on my pusher tug i want to run them off 12v  I'm not 100pc what  the bulb voltage is i think 4.5 drains battery quick
Logged

Faraday's Cage

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 332
  • Change is inevitable, except from a drinks machine
  • Location: Staffordshire
Re: voltage reducer
« Reply #1 on: April 07, 2008, 09:55:52 PM »

TT,

Not sure exactly what you're trying to achieve here. I assume you want to run your lights using a 12 volt battery.

What voltage are the lights (6v/12v etc.)  Do you know the wattage of the lamps or what current they draw ?

Grain of wheat lamps are somewhere in the region of 30mA  - 60mA each which would make around 600mA  - 1.2A total current.

FC
Logged

malcolmfrary

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 5,529
  • Location: Blackpool, Lancs, UK
Re: voltage reducer
« Reply #2 on: April 08, 2008, 11:25:54 AM »

It is important to know just what king of lights you are using, as each type will have a different answer.  Knowing what size the boat is would help as well, because the bulk and weight of any answer is an important factor.
An LM7805 will drop 12 volts down to 5 volts and has a limit of 1 amp, BUT dropping 7 volts at 1 amp gives 8 watts to get rid of, and this will make for a large heatsink.  Depending on your bulbs, you might need more than one, along with extra heatsinks.  This could mean that a separate battery for lighting is a better option.
Logged
"With the right tool, you can break anything" - Garfield

tubby tomo

  • Guest
Re: voltage reducer
« Reply #3 on: April 08, 2008, 08:04:50 PM »

 ???hi thanks for the response i have a large pusher tug 52" wait is no prob i think the the bulb are 4.5 there's 20 on the boat a 5v is to much  run anything less and the lights drain battery quick what i wanted to do was us 12v then gradually increase power to the right brightness just like a speed controller  do you think it can be don  many thanks ( tubby) :
Logged

StarLocAdhesives/FiveStar

  • Guest
Re: voltage reducer
« Reply #4 on: April 08, 2008, 09:37:01 PM »

You can do a variable voltage, adjustable with a variable resistor using a lm317 , we used to do one as one of the MB Leisurecraft electronics range

the link below has a calculator for the resistors , just make one of them a variable resistor/pot of around the correct value and you can adjust it

easy to make one up,you dont need to bother with a circuit board or anything , just solder wires to the pins and heatshrink them, or push the  components through cardboard or ply, then solder the wires together

http://www.reuk.co.uk/LM317-Voltage-Calculator.htm
Logged

Umi_Ryuzuki

  • Guest
Re: voltage reducer
« Reply #5 on: April 09, 2008, 03:34:36 AM »

Our club has been using these...
http://www.queensown.org/technical-data-sheets-5.html

They need to be heat sinked...


Also http://modelfireboats.com/homepage.html has some
great electronic tutorials and schematics....
http://modelfireboats.com/ue/index.html

 8)
Logged

tubby tomo

  • Guest
Re: voltage reducer
« Reply #6 on: April 09, 2008, 08:22:14 AM »

hi    thanks for your help ill get my son to have a look at the print out hes OK with electronics i just have give him a prod to make something thanks again ( tubby) O0
Logged

malcolmfrary

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 5,529
  • Location: Blackpool, Lancs, UK
Re: voltage reducer
« Reply #7 on: April 09, 2008, 04:11:57 PM »

If you can arrange your bulbs in strings of three, they should be happy with a nominal 12 volts, and the current should be more manageable.
There are devices out there that have a 12 volt input and a lower voltage output without generating a lot of heat, but the devil is in the price (probably).  If you measure how much current one of the bulbs takes for an acceptable light output, again, we should be able to come up with some sound suggestions.  If all the bulbs are in parallel, the total current will be twenty times that of one, whether off 4.5 volts or 12 volts and regulated.  Best guess at the moment is three or four high capacity Nicads or NiMH cells for the lights, purely to keep it simple.  Lights have a distressing habit of taking more power than the main motor.
Logged
"With the right tool, you can break anything" - Garfield

Umi_Ryuzuki

  • Guest
Re: voltage reducer
« Reply #8 on: April 09, 2008, 06:55:34 PM »

Logged
Pages: [1]   Go Up