Author Topic: LED advice please  (Read 274 times)

Offline thenoizeguy

LED advice please
« on: May 22, 2018, 10:37:23 PM »
Hi.
I want to add backlighting to a vintage tuner ( this model didn't have any ), with LED's.

I presume LED's are 3 V ?, and if so, do I wire 4 in parallel on a 3V power supply, or in series on a 12V supply ?

I have done something similar a few years ago on a Yamaha amp, where I used a separate power supply which I mounted internally and wired to the main switch.

Also, where is the most convenient place in Jhb where I can get small 12V or 3V chassis mount power supps ?

Thank you.
Expensive cables come in fancy silk lined wooden boxes to make you feel better about spending a fortune on them.

Offline fdlsys

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Re: LED advice please
« Reply #1 on: May 22, 2018, 11:22:03 PM »
Google LED calculator.
You can run LEDs from whatever voltage(s) you pickup inside the tuner, even directly from the secondary taps (AC) - it's a diode. But rather use DC from the tuner PSU.
Put LEDs in series so you will need only one current limiting resistor. Use calculator to work out the resistor value. Most old style LEDs are between 1.8-2V, around 20mA current. If unsure what type of LEDs you have, use lower V and mA as parameters to calculate the resistor value and then test.
If common red/yellow/green LEDs burn very brightly, they won't last long.
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Offline Steerpike

Re: LED advice please
« Reply #2 on: May 22, 2018, 11:37:43 PM »
It's a bad idea to parallel LEDs, unless each gets its own series resistor, since they are never closely matched enough to ensure equal brightness over time.

If you run LEDs from AC - unless full wave rectified - they will flicker. It's subtle, but noticable.

Offline JANNAS

Re: LED advice please
« Reply #3 on: May 23, 2018, 09:05:44 AM »
Use a single diode 400x in series with the dropping resistor, the led wil last much longer and does nor flicker.

Offline fdlsys

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Re: LED advice please
« Reply #4 on: May 23, 2018, 12:28:45 PM »
Which colour LEDs do you plan to use?
If it's for your Sansui, any colour will look good reflecting from the white scale.

Bring the tuner over next time, we'll hack it quickly. I have LEDs and resistors. (As well as hammers in all sizes... :giggle:)
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
Come back when you’ve lived a little. Miles Davis

Offline thenoizeguy

Re: LED advice please
« Reply #5 on: May 23, 2018, 07:52:12 PM »
Yes. The TU217.
Warm white should do it  :thumbs:

Call you Friday  :dop:
Expensive cables come in fancy silk lined wooden boxes to make you feel better about spending a fortune on them.

Offline fdlsys

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Re: LED advice please
« Reply #6 on: May 23, 2018, 09:35:58 PM »
:thumbs:
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
Come back when you’ve lived a little. Miles Davis