Awesome LED Level Meter




About: I like electronics.

This WAS going to be my entry to the 'Get the LED Out contest', but I was too slow.

I was bored one day. I wanted to build something cool. A quick bit of brainstorming and nothing came up. Digging through my junk boxes, I found a old level meter kit. I went over my mate's place later that day and we were having a killfest in Halo 3. He had seen this Level kit in use before, and wanted it rebuilt into a full-blown system to complement his surround system.

Here I'll guide yo on how to make your own.

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Step 1: Parts

For this Project you will need:

Scrap wood
LED level meter kit (available here)
LED's of your choice.
power supply
Diodes (if using AC output supply)
10 X BC558 or similar transistors.

Step 2: Tools

You will need the following tools:

Spray Paint (optional)
Soldering Station
Wire Cutters

Step 3: Power Supply

The kit I used Needed a supply at around 9 - 13 V DC, at up to 250 mA. I had a 12V AC 280mA Plugpack (also called wall-warts) sitting around. But the circuit called for DC. What to do?

The solution was for me to make a simple diode bridge (bridge rectifier). It uses just 4 small power diodes.

I layed them out, soldered them together, added a supply and viola! 15V unloaded. Perfect!

Step 4: Transistors!!!

Now onto the kit. It originally had 3mm LED's but these had to be removed. After that, I examined the circuit. The LED's originally used a common positive and the chip switched the outputs low to light the LED.

This meant I needed a PNP transistor.

Enter the simple but effective BC558. Actually anything will do here. Everyone should have plenty of these in their parts drawers. If not, well, you'll need to go get some. 10, in fact.

After finding them, you'll need to cut their leads into a special shape. Not 100% necessary, but makes life easier.

See pictures for more info.

Bend the collectors to 90° behind them. Slot them into their respective holes and solder them in.

Step 5: Wood

I used wood as stands for the display. You can use other stuff, but I had a scrap shelf lying around.

Using your jigsaw, cut them into pieces about 5cm wide. Mine are about 50 cm long.

Mark the positions of where you want your LED's. Mine splayed up at the top, away from the TV.

Drill the holes using a bit the same size as your LED's.

NOTE: I had 5 mm bulbs, and i managed to find a bit that was like 4.9mm. The LED's fit very snugly into the holes, so no glue is required.

Clean up the holes, and then if you want, give the front a quick coat of matte black spray paint.

Leave the planks aside to dry.

Step 6: Wiring Up LED's

After your pieces of wood have dried, it is time to insert and wire up the LED's. Push the bulbs into the rear of the plank. If they are slightly loose, put a drop of PVA glue on the rear. They hold in well.

bend the leads as shown in the picture. Then add a common ground line.

TIP: I had some solid-core Cat. 5e Ethernet cable nearby, so I pulled out some, removed the insulation and soldered it onto the cathode of all the LED's. Notice the small loop on the ground line. This is to make connection easier.

Step 7: Finished!

See pictures. Connect power, wire up an audio source, and plug in. Looking sexy!

Please comment.

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    21 Discussions


    8 years ago on Introduction

    Soo a few things

    1. What's the potentiometer for?
    2. What is the audio input source? Like a regular 3.5mm input jack?


    8 years ago on Introduction

    hey what's the difference with these two chips? LM3915 IC chip LM3916 IC chip


    Reply 11 years ago on Introduction

    yeah, just make sure your transistors can handle it. even better, replace the LED's with relay's. then you can put as many lights as your relay can hold!!! I'l send you a circuit diagram if you want.


    Reply 9 years ago on Introduction

    If you did make a circuit diagram, would you mind sending one my way too?  I love this idea but really want to make one with a bunch of LEDs per sounds level!  Thanks


    11 years ago on Introduction

    Dude, you're freaking awesome! Your stuff is amazing, I really like it, I hope to see more, this one is just really cool. Maybe you should have made the LEDs rainbow colored? No-- even better. RGB. Nice job anyways, I just have 3 more things to say to you. 1) +1 rating. 2) (added to favorites) 3) You should post an Instructable on how to make fudge.

    3 replies

    Reply 11 years ago on Introduction

    you like it? ok then, be prepared for an onslaught of instructables. Turbocharged go-karts, remote control docks, huge cinema displays, and awesome spud cannons. My aim is to get featured, as it will greatly boost my pageveiws. I'm in a contest against myself. You have been warned!


    11 years ago on Introduction

    Where's the project schematic? Where's the (BC558 or equivalent) transistors in the parts list? Your instructions in step 4 don't say what side is up when you cut the leads and the pictures are hard to see that the flat side is up when cutting the right 2 leads (base and emitter) short. For anyone substituting transistors, be sure of the pinout, since the 2N3906 has a reversed (EBC) lead order from the BC558 (CBE).


    11 years ago on Introduction

    It would be great to stick one of these in to the case of a pair of speakers behind the mesh that covers the cones. Would look fantastic on a guitar amp too!

    1 reply

    Reply 11 years ago on Introduction

    yeah. this design is so flexible. once you have built the board, you can mount it anywhere. it is only 80mm x 28mm x 9mm. The led's can be aranged in any order, too, so it doesn't have to be 1 - 10. I have done before 5,8,1,3,7,6,2,9,10,4. it looked really cool.


    11 years ago on Introduction

    My favorite bit was the hack to stick a transistor's base-emitter pair into an LED hole, leaving the collector for switching a bigger load.