What do I call this thing?? Help me name it, so I can search for it :) - Page 1
Forum section: electronics / beginners

author: Twellmann
author_rank: Newbie
timestamp: December 07, 2010, 11:32:10 pm
content: So, I find myself needing a simple circuit, but I havn't got a clue as to what it's calledI hope that, if I describe the circuit you can help me name it.Description:You have all used/built/seen this thing; there is a simple push button, and everytime it is pressed the circuit changes state/output.All of the states are cyclical, meaning that when you reach the last state, and press the button again, it returns to the first state.This type of circuit is found on numerous toys, hifi's and the like. Eg. when you press the source button on a tv-remote, it cycles between all the sources again and again.I need three these states:Both outputs offOutput 1 on, Output 2 offOutput 1 + 2 onThe outputs will drive a miniature 5-12V relay eachThanks in advanceDaniel

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: December 08, 2010, 12:01:44 am
content: Oh no .. it does not work that way .QuoteI have see such designs in Disco light systems.Basically , you are NOT looking for one part solution , but for an complete circuit .They must called as " opto-coupler switches " the IC at list , and I had found some in high end preamp's.Instead of mechanical switches on the sound inputs , they use those , because it eliminates sparks and noises caused by common mechanical switches . ( Input selectors )I do not have an schematic to share , but lets hope that my reply will help you , even by just a little.

author: tyblu
author_rank: Frequent Contributor
timestamp: December 08, 2010, 12:09:53 am
content: A state machine. The usual method for arriving at a logic circuit to realize this is to write down all of your inputs and outputs, describe their values for each state, draw any possible paths between states, then implement those paths with logic functions. There are other methods for minimizing the resultant logic circuits. Is this what you're thinking of?

author: Balaur
author_rank: Unknown
timestamp: December 08, 2010, 12:11:25 am
content: Hello,So you need some kind of machine with a finite number of states. Hmm...Without knowing any details of your implementation goals or target, here is a suggestion:You can use discrete logic ICs and implement a Shift Register Counter (or more precisely a ring counter) with three flip-flops (ff0, ff1, ff2). The output of each flip-flop represents the corresponding state. If "high" then the state is active.Each primary output is activated by a relay driven by a BJT transistor (with a protection diode in parallel of course). The base is driven by the outputs of the flip-flops, but with a twist:- Use a diode from ff1 to output 1 transistor base- Use a diode from ff2 to output 1 base and another one to output 2 transistor base.(Note: According to flip-flop characteristics, you can also drive the relays directly)(Second note: a transistor-only implementation is also possible)However, please familiarize yourself with the wonderful concept of "de-bouncing" before proceeding.If you have experience and hardware to work with microcontrollers, you can also try using a cheap, 8-pin MCU.Cheers,Dan

author: Mechatrommer
author_rank: Super Contributor
timestamp: December 08, 2010, 04:56:57 am
content: i'll go with the mcu. here goes the ugly sketching...you'll need (N+3) pins mcu = Vcc, GND, input and N-output.number of state = 2^N.the cap is for debounce i think, but i could be mistaken.instead of directly connecting to relay, you can use bjt to cope with higher current if necessary.

author: Simon
author_rank: Unknown
timestamp: December 08, 2010, 06:33:57 am
content: I think he might be looking for something like a binary counter and then a decoder to activate one output at a time, or perhaps a shift register can do it ?

author: oPossum
author_rank: Super Contributor
timestamp: December 08, 2010, 06:45:08 am
content: 74HC4017 Counter/Decoder

author: Simon
author_rank: Unknown
timestamp: December 08, 2010, 07:30:44 am
content: just the job

author: oPossum
author_rank: Super Contributor
timestamp: December 08, 2010, 09:39:51 am
content: Schematic

author: Twellmann
author_rank: Newbie
timestamp: December 08, 2010, 11:38:16 am
content: It seems we have a winnerThis looks to be the exact thing I need. What do you suppose the current draw is? TheV+on the relay coil is for the rated voltage of the coil, right?I think I should make a complete description of my project, as I still have a few more questions.EDIT:I've created a thread for the complete project over here:https://www.eevblog.com/forum/index.php?topic=1931.0

author: oPossum
author_rank: Super Contributor
timestamp: December 08, 2010, 01:18:00 pm
content: The current draw of the 74HC4017 is under 10 uA. When one or both relays are on, then the current will be a few mA (to drive the ULN2003) plus whatever the relay coil(s) need.If you don't have a 5V supply already present, then using a CD4017B and ULN2004 may be better. They will work with up to 15 volts.Revised schematic for 12V supply and four steps (off/off, on/off, on/on, off/on).

author: Twellmann
author_rank: Newbie
timestamp: December 08, 2010, 03:26:44 pm
content: Quote from: oPossum on December 08, 2010, 01:18:00 pmThis is really great, if I want to keep the three states on the 12V circuit, can I then instead of the fourth output going to the transistor-array, loop it back to the reset pin? Basically keeping the layout from the 5V layout