PCB Prototype $2 for 10 PCBs (Any Color): https://jlcpcb.com
https://www.patreon.com/julian256
The green LEDs are far too bright (probably gallium nitride types). The bottom LED stays on in dot mode. Nearly had an incident with a reverse connected tantalum capacitor too 🙂
Negative Voltage Dual DC12V -12V Power Supply Module 5-12V to ±12V For Amplifier https://ebay.us/1uutVv
https://www.patreon.com/julian256
The green LEDs are far too bright (probably gallium nitride types). The bottom LED stays on in dot mode. Nearly had an incident with a reverse connected tantalum capacitor too 🙂
Negative Voltage Dual DC12V -12V Power Supply Module 5-12V to ±12V For Amplifier https://ebay.us/1uutVv
that link to the 5v to – and + doesn't work anymore which is a pity as i have always wanted a cheap way to get split rail voltage from batteries. Ironic that too bright leds is a problem in 2019 in the 1980s was always a problem that they were too dim
The results of swapping the red and black was so satisfying lol, I'd better go book an appointment to talk about that 🙂
Maybe you can team up wit lookmumnocomputer… he would probably build your whole device in a couple of days^^
Try 860R resistors instead of 470R.
I made a multiplexed stereo version when I was 15 (30 years ago) in my electronics course. Mine uses 2 op-amps for inputs with level VRs for input adjustment, works on 5V only and is sat right here with me bouncing to your voice lol. Thought id dig it out and power it up via usb battery supply to see if it still works. It does! 30 years on! lol My 30 year old green led's suffer the same issue on the first dot if there is audio but they are only just BARELY visible. Im not sure but my driver could be the LM3914 given its age. It only uses the one LM chip and for the life of me I can't remember how it is multiplexed to 2 channels but it does work. I'm sure it was a project from a very early Electronics magazine as mine is on hand drawn etched pcb which we had access to in the course, it looks scruffy and botched but hey, it works lol. The op-amps in mine are a pair of CA3240E .I can't tell the other 2 chips but I am sure one is a 556 timer and one is an analogue switch IC driving the 2 'bars' in a 1,2 sequence via 2 transistors and feeding the LM chip from the analogue switch IC, as my PCB is mounted upside down and bolted in, in a VHS plastic "book" case it is hard to see lol Although I am sure the PCB you have will have the proper components for its design, the input to an LM3914/5 should be a regulated audio signal (DC) as it can be fussy about AC Audio in dot mode. I would try a different green LED for your set up as the current limiting is done by the LM3915 its'self and be careful not to go above 7v on the mode input as it can warm up the IC somewhat 🙂 As mentioned the leakage on pin 1 can be 150uA but may be as high as 450uA which would be more than enough to light your green LED at that brightness.
I can't make these but I want to put it on my robot
You could use colours from computer power supplys!
You need to paint the tops of the leds with a dark color sharpie maybe a blue to add some tinting
think u can buy little vu meter kits like that on ebay for pence mate or do they need to be certain dimensions etc
Maybe the resistors were chosen for GaP green LED's and was supplied with InGaN ones instead?
Those pins are so easy to swap out. What pev and Mark said. +12 is Yellow; +5 is Red; 0 is Black and use White for -12. (AT Motherboard is Blue for -12v; but you don't have blue, now, do you.) 🙂 We will go with whatever you choose Julian. In your defense, electrons are color blind. I am so glad you are "chipping away" at the Vocoder. I can't wait to hear it produce awesome sounds. Love your videos, Julian!
Maybe change the 5V supply for the LEDs to 3.3V or just use a 2W resistor of suitable value (you'll need to experiment with different values) in series on the 5V. I built a stereo LED VU meter many years ago using the velleman VU meter kit. 2 boards and all the LEDs and other components are included. I put it in a transparent plastic box with RCA connectors on the back. Its powered from a single +12V AC/DC wall adaptor. It works very well.