Instructables

How to backlight a audio video receiver volume knob. (onkyo hr550)

Backlit volume knobs are a somewhat of a recent creation. There really is no functionality in it, but it looks great.
i got a hr550 receiver for chistmas, and decided to throw up a tutorial on how to do this.

Items needed:
Multimeter
Soldering iron (solder, flux)
hot glue (ultra high temp.. if you do not have a 220watt glue gun and high temp glue, skip it. the amp gets extremely warm, and melted glue and components just dont mix)
clear acrylic plexiglass sheet (cd cases will work just fine)
heat shrink tubing
wire
leds
resistors
Drill
holesaw
(reflective flashlight bezel/aluminum duct tape optional-only for brightness)


(I unfortunatly finished my project prior to taking pictures of it, so some of the steps are already accomplished)
 
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Step 1: Wiring the LEDS/Power Source

**WARNING**
You will be working with electricity that can kill you.
If you do not know how to solder, do not do it. Learn how to do what you need to do first, so you dont end up ruining the project. there are a number of 'how to solder' tutorials in instrucables.com.
If you damage something, youre on your own. The only person that should take the blame is you.
**END WARNING**

Obviously, the first thing you need to find is a power source.
I wanted the backlight to turn on when the receiver turned on.
remove the case and look towards the sirius/xm radio inputs. Both these inputs carry a low voltage power source, and is ideal for the leds.
If you are using sirius, do not tap it for power, look somewhere else.

LEDS

I salvaged some leds from a rope light i bought on christmas clearance. ($1.90 for 150 led rope).
I had no idea what the forward voltage or current of them.
There is a trick to measure the forward voltage by soldering a 1k ohm resistor to the positive lead, hooking it up to a 9v battery and using the multimeter, determine the voltage. (it will drop by exacly 1k ohm) Once again, there are plenty of tutorials on how to use a mutlimeter to find these things out.

On the current factor, you basically have to take a guess. This site has a basic overview of what certain leds are:
http://www.kpsec.freeuk.com/components/led.htm

After you find a general starting point with that information, head to http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm and plug in the info.
This will tell you what size resistor you will need.

(never mismatch leds. If you mismatch them, you may have an issue of using the wrong resistor and watching the lower voltage of the leds burn up)

I determined my leds were .60ma at 3.5volts each. (total of 3)
add up the volts-11volts total
12volt power supply
I need a resistor that is 820ohms at 0 watts

(sorry the picture quality on this isnt the best.. new camera, havent had much time to figure the settings out)
drewdoog (author) 5 years ago
Its been a year since I did this, and its still problem free.
superjames5 years ago
Pretty cool! Where exactly did the LED go? inside the hole you drilled? or just behind the plexi?
drewdoog (author)  superjames5 years ago
inside the hole behind the plexiglass
stigg6 years ago
I just saw this. Thanks for the insperation to do something about mine. Its the only cabinet component that is not blue LED themed. A resistor and some LEDs from radio shack looks like it would do the trick. I have a question. On my 605 the unit has a remote control key for the Dimmer function. It works on the front LCD. It looks to be very close to the 705 which has the blue LED and I am wondering where I could look to tap the defualt power source for that. Any ideas?
drewdoog (author)  stigg6 years ago
If i were you, id skip radio shack for the LEDs. for a single blue led at radio shack its $5... I do not know what you are talking about with the dimmer led. The easiest way to find a power source is with a autoranging multi meter. remove the front panel and just start probing.
That looks really awesome. I do not have this thing though, but many people might, and this could definitely help them. Nice job.
drewdoog (author)  GorillazMiko6 years ago
It was a fun project to do. I really had no clue what I was doing but I knew it could be done. I will have to update this with better pictures some day.
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