I wanted to make some bar-graph displays, and I have a small tray of various 10-segment bar graph led's I'd like to use. Unfortunately, I have 74hc164 shift register, handles 8 pins. I have a 16 channel 74hc4067, which would leave me 6 pins to do whatever with - except I can't do (2) 10 segment displays with the 16-mux.
I feel like this is the trick at the store where they sell you pack of 10 hot dogs, and 8 rolls....
Yes I can buy 8-segment graph displays. If anyone's shopped for them - you already know it's like (10) 10 segment graphs for $12 OR I could buy (2) 8 segment graphs for $12.
Do they make 10 segment shift registers or mux or 20 segment ones?
The LM3914 in linear.
The LM3915 is log (e.g. for sound).
There is also the LM3916 (VU meter).
Old technology. I think I used them already in the late seventies.
Leo..
Yes, I was looking for something simple and easy. Reading more about them, I can see it's not as obvious as I assumed it would be. I will just use 8 segment graphs, and leave these 10 segment ones for something else.
MarkT:
You can also Charlieplex a 10 digit bar-graph display from 4 pins, or 2 10 digit's from 5 pins.
Good suggestion.But only to light one led at a time. However, you can combine the technique with multiplexing to light multiple leds, but the brightness will be much lower. To overcome low brightness, you can add transistors. This will make the wiring and coding more of a challenge, but we can support with that.
I'm better off using 10 segment display for status indicators, than fill up a board with all that extra stuff and code - instead of using 8 segment graph. Or use 16 channel mux, and find something else to do with 6 other pins. If I have to populate a 3" square area just to use 10 instead of 8, it is just not worth it.
They got these neopixel led strips with all the circuits built onto it, I can do pretty much anything with an existing library and just a few blocks of code. And it looks like I can buy individual addressable RGB led's that I can arrange in any number wherever I want.
They're useful for status leds, or stick on a solderless breadboard to test with. Maybe use the 8 segments, and the first segment as a power indicator. Maybe use 1st and 10th segment for a blinking low-battery warning. Some of the graphed 10 segments are multi-color, and 2 segments on the top or bottom are different colors, so it's possible to use those for errors or other signal display - outside 8 segments for a graph level.
My only purpose to use them was that they are less expensive than 8 segment graphs. From a distance 2 segments aren't going matter. When it comes to larger graphs they get expensive.
There are "BCD to 10 pin" decoders: CD4028, 74xx145, 74xx42, etc... Here's a digikey search page
I don't see any 10bit shift registers, but there are some 12bit versions in SOIC-20. HEF4894. These seem to be about the same price (> $1) as a small microcontroller that could do the job as well.
QTY (10) CF4028 in DIP package, on eBay is $2.25 w/ shipping. Perfect. Thank you.
But the devil is in the details. The data sheet explain "ONE OUTPUT AT A TIME" current at .88 ma at 5 volts or 6 ma at 15v. So I would have to pulse output rotate between all segments, and drive the output to a bank of 10 transistors (or transistor array/bus if they even exist).
I think the max current on 74ls145 is 1 ma.
74hc42 If I read correctly - output current is 20 ma - but I didn't read the whole thing, to find the surprise booby trap. (eBay cost qty: 2 @ $.93)
QTY (10) CF4028 in DIP package, on eBay is $2.25 w/ shipping.
ATmega8's are cheaper (oops. Missed the Q10 part; m8 is ~$8 for 10 pieces.) Shucks, "Pro mini" clones are cheaper
The ATmega8 has better drive capability, can be customized to do either bar- or dot- style displays, and probably handles 2 bargraphs (2x4 inputs, 10x which led, 2x which bar = 20 pins)
This is making life so hard! Just use a max7219. Drives up to 64 leds, 1 chip, 1 resistor, 2 caps, 3 Arduino pins. More chips can be daisy-chained using the same 3 pins.
