looking for IC, don't know what it's called. - Page 1
Forum section: electronics / beginners

author: made2hack
author_rank: Frequent Contributor
timestamp: June 10, 2017, 03:33:00 pm
content: Hey all,I want an IC that does the following:- I press a button, and the output goes from say pin 1 to pin 2 to pin 3 and back to 1 (or something to that effect). I want brightness control by essentially having a + and - button that cycles through a pre determined number of outputs and I don't want to use a micro.However, I don't know what this type of IC is called.Thanks,

author: stevelup
author_rank: Regular Contributor
timestamp: June 10, 2017, 03:41:28 pm
content: Decade Counter?

author: ^_^
author_rank: Regular Contributor
timestamp: June 10, 2017, 03:42:13 pm
content: Logic counter / counter shift register ?

author: daqq
author_rank: Super Contributor
timestamp: June 10, 2017, 03:42:24 pm
content: Well, a Johnsons (ring) counter (4017) with switch debouncing stuff might do the trick.

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 10, 2017, 03:44:35 pm
content: I don't fully understand what you want but maybe an up/down counter?They come in binary or bcd, not sure if there are any decimal output ones but you can always decode to decimal.http://www.cmos4000.com/cmos/4192.html

author: P90
author_rank: Frequent Contributor
timestamp: June 10, 2017, 04:01:53 pm
content: If I understand correctly perhaps a 74HC595 shift register IC?

author: kony
author_rank: Regular Contributor
timestamp: June 10, 2017, 04:18:23 pm
content: 4017 with reset fed back from fourth output +mandatorydebouncing of the button input.

author: ebastler
author_rank: Super Contributor
timestamp: June 10, 2017, 05:02:07 pm
content: Debouncing your switch, initializing the counter, getting the right output pattern (one active output only at any time, three states), etc. adds complexity pretty quickly. I read in the OP that you don't want to use a microcontroller, but if you want a simple circuit some little 8-pin PIC or similar is probably the way to go.

author: rdl
author_rank: Super Contributor
timestamp: June 10, 2017, 11:14:11 pm
content: A 4017 should work. It will be good for up to 10 steps but won't be able to reverse, just wrap around to beginning. It has a Schmitt trigger input, so debouncing should be easy. All it will provide is outputs though, you will have to add whatever circuitry is needed for controlling your lights and their brightness. That part will depend mostly on whatever type of lights you use.

author: made2hack
author_rank: Frequent Contributor
timestamp: June 11, 2017, 11:11:23 am
content: Ok, thanks all.In principal, the idea is that for each press of a button, my idea was that the ic would jump from one resistor to another. That resistor would change the PWM from say 25% - 50% - 75% - 100% Duty and drive the LEDs.However, since it would require 1 - the 4017 decade counter and a PWM signal (maybe from 555), perhaps as ebastler mentioned, maybe i should throw an 8-bit msp430 or similar that could do it all. That way I won't need either a decade counter and a 555 timer either.

author: stevelup
author_rank: Regular Contributor
timestamp: June 11, 2017, 12:54:32 pm
content: Well yes, an MCU would be massively simpler for this task, take up less space, be more capable and in the end, probably cheaper. But you said you didn't want to use one!

author: made2hack
author_rank: Frequent Contributor
timestamp: June 11, 2017, 01:26:00 pm
content: Yeah, I tend to want to favour "passive" components if possible just because I feel that MCUs can be at times overkill.However, in this case, it might be a cheaper option.

author: tooki
author_rank: Super Contributor
timestamp: June 12, 2017, 02:29:38 pm
content: Small MCUs are so cheap that they areveryoften cheaper, especially once the cost of discrete ICsandthe needed passives are factored in. Add to that that the MCU can be easily programmed to do things that would be very expensive to do with discrete components, and you see why they're now everywhere.

author: ziggyfish
author_rank: Regular Contributor
timestamp: June 12, 2017, 03:53:08 pm
content: To answer your question your looking for two ics decoder + counter. However as others have stated an MCU is a better and cheaper choice ($0.35 vs $1).

author: daddylonglegs
author_rank: Contributor
timestamp: June 12, 2017, 04:58:18 pm
content: I agree with the people saying that:You will need to debounce the buttons, either in hardware or in firmware.A micro-controller will give you the smallest and cheapest solution.But there are other solutions, including the counter solution you are asking for.Another: Some digital potentiometers are supplied with debounced up/ down inputs, eg AD5116, MAX5456. Using that to command an op-amp + MOSFET based current sink would give you fine control over the LED current (perhaps too fine, 64 presses to reach full brightness).https://www.maximintegrated.com/en/products/analog/data-converters/digital-potentiometers/MAX5456.htmlLog taper.http://www.analog.com/en/products/digital-to-analog-converters/digital-potentiometers/ad5116.htmlLinear taper (I think).

author: Cliff Matthews
author_rank: Unknown
timestamp: June 12, 2017, 06:11:00 pm
content: If you've already tested something with a 555, then RC average the 555's PWM to quad comparator driving the LED's. Fiddle with the resistor ladder to get the right display. I know it's cheap old-school stuff *edit here's a better example: