Electronics help please !

[alarmeng]

Hi Guy's im after a little help as ive &%$? two up already :-)

Im building a display board and im using these led/switches (Dear i know but thats whats wanted.

http://docs-europe.electrocomponents...6b80e2ad10.pdf

Reading the doc it says i need a limiting resistor ?? Im struggling with the value to be honest but theres a little more.

Could i not just use an LED trans former ? If so would i need a limiting resistor?

Also i want to connect 6 up in parralel so would i need a different value?

Also would it be possible to run from a 12vdc source which would need dropping to 4.6v.

Is any of this possible as i dont fancy blowing any more up .

Many thanks in advance

Gaz

[Meat-Head]

HUH! Daddy (before he died) told me about this when was a toddler.

If you want to run an LED off 12 Volt, use a 1K resistor. As lookin at your last posts you seem to be a leecher, with more posts than downloads.

Or if you really fussy then use a LM317 Regulator

Good bye

[alarmeng]

HUH! Daddy (before he died) told me about this when was a toddler.

If you want to run an LED off 12 Volt, use a 1K resistor. As lookin at your last posts you seem to be a leecher, with more posts than downloads.

Or if you really fussy then use a LM317 Regulator

Good bye

Many thanks for that (Why the commet about being a leecher fella ?)

[icepick]

Maybe not what you want now,but one to put in favorites!

LED series parallel array wizard

Regards

[TheCoder]

Depends which switch you are going to use.

From what i've read on the datasheet there are two kinds - one type with a limiting resistor built in for 5V operation an the other type with no limiting resistor at all.

With the non-limiting one I cant see any details for Vf for the the various colours but generally red are around 2Vand green around 2.1v, blue around 3.6V and white around 3.6v. If you want to run from 12V with 20mA then you would need a series resistor of -

(12 - Vf) / 0.02

so, for red (vf=2v) you get (12-2)/0.02 = 500 Ohms

The other thing to bear in mind is the power disipated by the resistor. In this case your dropping 10v @ 20mA so, using W=VI, that would be 10 * 0.02 or 200mW. I'd recommend a 1/2 Watt resistor for this task.

If you use the 5v switches (these already have a resistor built in) you can run from 12 just by adding another series resistor, just take the Vf as being 5v

If you dont want your LED's as bright then just reduce the current from 20mA. 10 or 15mA may be adequate for your purposes. The only real way to know whats best for your circumstance is to try it and see. Just dont go too far over 20mA.

nb, you wouldn't want to be using transformers fow such a task - way too complex and expensive. Voltage regulators would also be a waste of money for such a simple task. Resistors are maybe tuppence each whilst a regulator would cost you 20-30p !

[alarmeng]

Hi Coder

Many many thanks for that im getting it now.

Appreciated, im going to have to rewire things now but i think i have it sussed.

Also ICEPICK cheers for the link :-)

Gary

[tshirtman]

(Why the commet about being a leecher fella ?)

Meaty's pizzed off coz tracy's up the duff, again.

[Meat-Head]

Meaty's pizzed off coz tracy's up the duff, again.

Mutter moan, mutter.

OFF TOPIC:-

Found this though, thanks for mentioning it

Kate Ford