Toby
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Registered: 29th Nov 05
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I have a simple 5v circuit (actually i may be running it a lower than that but not sure yet) i need a simple rocker switch to turn it on and off
will this do? its rated for a lot higher voltage so wandering if my trickle of a voltage will not be able to flow through it or whether it will be just fine?
http://www.maplin.co.uk/Module.aspx?ModuleNo=98091
Edit - I now something to reduce my voltage from 5v to about 3.5/3v. Im guessing something along the lines of a resistor? any one point me in the right direction
[Edited on 12-02-2009 by CorsaB4ever]
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csweatherston
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Registered: 16th Jan 06
Location: Devon
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will be fine.
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Toby
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Registered: 29th Nov 05
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cheers mate
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Toby
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Registered: 29th Nov 05
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see edit
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Dom
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Registered: 13th Sep 03
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You want a regulator to drop the 5v to 3/3.3v. If the max load is 1A, then something like TS1086CZ-3.3 (maplin code - N57CA) should do the trick 
you can bodge it with resistors, but if the 5v line drops (or increases) so will the output. With a reg it'll try and keep a consistent output.
edit - you'll also need to add a few capacitors, eitherside of the Reg (ie: pos to gnd) to stable the output. And before you use it, obviously check it out with a desktop power supply and multi-meter.
[Edited on 12-02-2009 by Dom]
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Toby
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Registered: 29th Nov 05
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Cheers Dom! Can i get the capacitators from maplin also and if so could you possibly point out which ones? Could you also just point out where in the circuit i should place the regulator and capaciator, cheers
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Dom
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Registered: 13th Sep 03
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Similar to -
But the input is +5v, outputs +3.3v and the caps are 10uF.
Fit the switch before the first capacitor on the +5v side and the Fans pos on the regs +3.3v output (after the capacitor).
This should work, but it's been along time since i've done anything like this  Hence why i said you should check it with a bench power supply and multi-meter before using it.
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Toby
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Registered: 29th Nov 05
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so on my circuit starting form source i would have;
Positive from source - Switch - Cap (connected to neg) - Regulator (connected to neg) - Cap (connected to neg) - positive to fan?
this correct?
this ok in 10uf version?
http://www.maplin.co.uk/Module.aspx?ModuleNo=7011
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Dom
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Registered: 13th Sep 03
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All the negatives connect together (ie: Source neg, both cap negs, reg neg and fan neg). Then all the positives are connected together like above (ie: source to switch, then to cap 1 pos and then reg positive in. Then reg positive out to cap 2 pos, then to fan pos).
Remeber that the Reg has three pins, 1 is usually in, 2 is usually ground/neg and 3 is positive out. I doubt it'll get hot, but if it does you might need a heatsink (again, i can only see it getting warm). Also make sure you buy a reg that can deal with rating of the Fan - ie: Fan draws 2 Amps get a reg that can handle 2amps, Fan draws 1 Amp, get a 1A Reg.
And yeah that capacitor looks about right - 10uF should do it but you might need something bigger like 100uF or 10nF.
Like i say, make sure you get this running before you put it in your application as i'm working off ancient GCSE electronics
Unless you're local to a Maplins, i would see if parts are cheaper on Ebay/Rapid Electronics (can't remember if their delivery is cheap).
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Dom
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Registered: 13th Sep 03
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By the way, unless it's essential for the fan to run at 3.3v then it might be worth bodging it with resitors (keep adding them til you hit 3volts or so). Same goes if your using it with a clean power source - PC's PSU/Battery etc.
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Toby
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Registered: 29th Nov 05
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well the source is from my media players PCB so around 3 volts is just the aim so not really after anything to technical plus it wont matter that the resistor will take time to build up in other words my fan wont blow if it has the full 5v before the resistor kicks in. What resistors should i be looking at
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John
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Registered: 30th Jun 03
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There will probably be 3v somewhere on the board, micrcontrollers normally run at 3v.
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ed
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Registered: 10th Sep 03
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You could make a circuit using a 555 IC and a MOSFET to trigger the voltage. Could then even have variable speed control then...
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