How do I convert 5v dc -> 2.5v dc?
Don Fredricks
Mark Schwarz <ek...@cleveland.Freenet.Edu> wrote:
>
>Can someone tell me how to convert 5v dc (from power suppy) to 2.5v dc?
>The output is to power an LED on a computer panel to indicate power on.
>What is the simplest way? Some sort of resister. I am not an electronics
>expert, but I can use a soidering iron. Thank you...........
Mark:
I don't think you need to "convert" the 5v DC to 2.5v DC; you just need to
limit the current with a resistor in series....
--
Regards,
Don Fredricks
<fred...@gdesystems.com>
Mark Schwarz
Can someone tell me how to convert 5v dc (from power suppy) to 2.5v dc?
The output is to power an LED on a computer panel to indicate power on.
What is the simplest way? Some sort of resister. I am not an electronics
expert, but I can use a soidering iron. Thank you...........
/\/\ark.....
In real life - Mark Schwarz | Amiga 2000 / G-force 50 mhz /
msch...@erc.cat.syr.edu | 12 megs / EMPLANT Mac / A2386
313 Hixson Ave, Syr, NY 13206 | CD-ROM / EGS / ES-600C / DAT
Geoff Drayson
> Mark Schwarz <ek...@cleveland.Freenet.Edu> wrote:
> >
> >Can someone tell me how to convert 5v dc (from power suppy) to 2.5v dc?
> >The output is to power an LED on a computer panel to indicate power on.
> >What is the simplest way? Some sort of resister. I am not an electronics
> >expert, but I can use a soidering iron. Thank you...........
>
To power an LED from a +5v DC supply, you need to solder a resistor in series
with the LED, and ensure that the LED is connected the correct way round.
A typical resistor value would be 330 Ohms. ( anything from 220 to 470 Ohms
would be ok).
+ ---------RESISTOR--------|>|--- -ve
led
If you can't determine what way round to connect the LED, try BOTH ways.
The correct way will LIGHT the LED, the incorrect way round will NOT light the
LED, and will do no damage.
**********************************************************************
* Geoff Drayson <Ge...@ScopeSys.com> http://www.charm.net/~scope *
**********************************************************************
Christian Schlosser
>Can someone tell me how to convert 5v dc (from power suppy) to 2.5v dc?
>The output is to power an LED on a computer panel to indicate power on.
>What is the simplest way? Some sort of resister. I am not an electronics
>expert, but I can use a soidering iron. Thank you...........
You could use the appropriate voltage regulator... (I think they have
them from 5 -> 2.5. Or you might try something somewhat close like 5 -> 3
or something)
Lonnie C. Harger
says...
>
>
>Can someone tell me how to convert 5v dc (from power suppy) to 2.5v dc?
>The output is to power an LED on a computer panel to indicate power on.
>What is the simplest way? Some sort of resister. I am not an electronics
>expert, but I can use a soidering iron. Thank you...........
>/\/\ark.....
>In real life - Mark Schwarz | Amiga 2000 / G-force 50 mhz /
>msch...@erc.cat.syr.edu | 12 megs / EMPLANT Mac / A2386
>313 Hixson Ave, Syr, NY 13206 | CD-ROM / EGS / ES-600C / DAT
Everybody get back, I'll take this one.
Hi Mark. This is easy. Add a resistor in series the LED. The
value you want to use depends on how brite you want it glow.
Very brite = 220 ohms (red,red,brown)
Medium = 470 ohms (yel, vio, brown)
Dim = 1k ohms (brown,black,red)
200 to 1000 ohms is the general range to stay in.
--
Lonnie C. Harger
Northwestern University, Chicago IL. USA
lon...@calvin.medicine.nwu.edu
Geoff Drayson
In article <3r3ss4$4...@opal.cybergate.com>, <Unk...@scope.charm.net> writes:
> Path: news.charm.net!news.sprintlink.net!opal.cybergate.com!usenet
> From: <Unknown> (.)
> Newsgroups: sci.electronics.repair
> Subject: Re: How do I convert 5v dc -> 2.5v dc?
> Date: 7 Jun 1995 09:52:04 GMT
> Organization: Cybergate Information Services
> Lines: 43
> Message-ID: <3r3ss4$4...@opal.cybergate.com>
> References: <3r0srl$l...@usenet.INS.CWRU.Edu> <3r2dp8$i...@gde.GDEsystems.COM>
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>
> In article <3r2dp8$i...@gde.GDEsystems.COM>, fred...@gde.GDEsystems.COM (Don Fredricks) says:
> >
> >In article <3r0srl$l...@usenet.INS.CWRU.Edu>,
> >Mark Schwarz <ek...@cleveland.Freenet.Edu> wrote:
> >>
> >>The output is to power an LED on a computer panel to indicate power on.
> >>What is the simplest way? Some sort of resister. I am not an electronics
> >>expert, but I can use a soidering iron. Thank you...........
> >
> >
> >I don't think you need to "convert" the 5v DC to 2.5v DC; you just need to
> >limit the current with a resistor in series....
> >
> >
> >--
> >Regards,
> >Don Fredricks
> ><fred...@gdesystems.com>
> >
>
> 2 equal value resistors.
>
> You can use this voltage divider to half the voltage... now as far as
> current goes, you will need to figure out how much current you want going
> to your LED. By increasing the Resistance of the Resistors, you Decrease
> the amount of current going to your LED.
> __________________
> I | I
> | | |
> 5vdc R1 LED
> | | |
> | I________I
> | |
> | |
> | R2 R1 and R2 are of equal value.
> I_______I
>
> Now I'm sure that there are many that would argue that this includes an
> unnecessary resistor... Well, Let's just see if anyone objects..:);) .) :)
>
>
YES !!! I will <grin>
R1 is unnecessay, unless oiu WANT to draw extra current from the Power supply
!.
You only need R2.
LED are "current" devices, and normally have a rated/ optimum operating
current Iopt.
Assuming the LED has a forward voltage drop of 1.2 volts (typical for a RED
led), then there is 5-1.2 = 3.8 volts across the resistor R2.
Assuming a 10ma Iopt, then R=V/I= (3.8/10) K = 380 Ohms. Lets say 330 Ohms
and have a little more current !!!.
lir...@pinn.net
> In article <3r2dp8$i...@gde.GDEsystems.COM>, fred...@gde.GDEsystems.COM (Don Fredricks) says:
> >>Can someone tell me how to convert 5v dc (from power suppy) to 2.5v dc?
> >
>
> A voltage divider will allow you to tap 2.5 volts from a circuit of
> 2 equal value resistors.
>
> You can use this voltage divider to half the voltage... now as far as
> current goes, you will need to figure out how much current you want going
> to your LED. By increasing the Resistance of the Resistors, you Decrease
> the amount of current going to your LED.
> __________________
> I | I
> | | |
> 5vdc R1 LED
> | | |
> | I________I
> | |
> | |
> | R2 R1 and R2 are of equal value.
> I_______I
>
> Now I'm sure that there are many that would argue that this includes an
> unnecessary resistor... Well, Let's just see if anyone objects..:);) .) :)
>
>
>>>>
The resistor divider circuit using resistors is a perect example of an overdesigned circuit - all you need is ONE
resistor to limit current flow through the LED.
Samuel M. Goldwasser
>In article <3r0srl$l...@usenet.INS.CWRU.Edu>,
>Mark Schwarz <ek...@cleveland.Freenet.Edu> wrote:
>>
>>What is the simplest way? Some sort of resister. I am not an electronics
>>expert, but I can use a soidering iron. Thank you...........
>
>Mark:
>
>I don't think you need to "convert" the 5v DC to 2.5v DC; you just need to
>limit the current with a resistor in series....
>
an LED with a built in current limiting resistor.
--- sam
f...@unixg.ubc.ca
>In <3r0srl$l...@usenet.INS.CWRU.Edu> ek...@cleveland.Freenet.Edu (Mark Schwarz) writes:
>>The output is to power an LED on a computer panel to indicate power on.
>>What is the simplest way? Some sort of resister. I am not an electronics
>>expert, but I can use a soidering iron. Thank you...........
>
>them from 5 -> 2.5. Or you might try something somewhat close like 5 -> 3
>or something)
Regulator? Why? Just use a 120 or 150 ohm resistor.
LED draws around 20mA of current at around 2.2 volts, and
2.5 to 3 volts get dropped across the resistor, therefore:
5v - 2.2v = 2.8v (drop across resistor), and
2.8v / 20mA = 140 ohms
So, you can use either a 120 ohm or 150 ohm resistor, which are standard values.
Don't bother with a regulator, ridiculous!
-- !
Francis __o f...@unixg.ubc.ca Team OS/2 Canada
_`\<,_
(*)/ (*)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\ /~~~~~~~~~~~~~~~~~~~~
\_________ __________/
Mutant Mountain Biker ?
f...@unixg.ubc.ca
>Keeping in that you are not an electronics guru. Just use the simple
>single resistor in series with the LED.
>
> Resistor
> +
>-------------^^^^^------->|------ -
> 330 to 1000k ohms
>LED
I think you mean 330 to 1k ohms, not '1000k' ohms.
CMeJeff
Peter Frost
fred...@gde.GDEsystems.COM "Don Fredricks" writes:
> Mark Schwarz <ek...@cleveland.Freenet.Edu> wrote:
> >
> >Can someone tell me how to convert 5v dc (from power suppy) to 2.5v dc?
> >The output is to power an LED on a computer panel to indicate power on.
> >What is the simplest way? Some sort of resister. I am not an electronics
> >expert, but I can use a soidering iron. Thank you...........
>
> Mark:
>
> I don't think you need to "convert" the 5v DC to 2.5v DC; you just need to
> limit the current with a resistor in series....
> --
> Regards,
> Don Fredricks
> <fred...@gdesystems.com>
>
>
If it's a reasonably standard LED then a 150 Ohm resistor should suffice.
--
Pete Frost.
pe...@body.demon.co.uk