Solution without a MC? - Page 1
Forum section: electronics / beginners

author: mortos360
author_rank: Regular Contributor
timestamp: August 13, 2013, 03:49:42 pm
content: Here is what I need:When power is ON, wait a few sec. then turn on relay for 2 sec., then turn it off again.Usually I would solve this with the Arduino, but I was wondering if there is a another solution to fix it without a microcontroler?

author: c4757p
author_rank: Super Contributor
timestamp: August 13, 2013, 03:52:57 pm
content: I am a fan of tiny microcontrollers like PIC10F200 to handle things like this. Long time durations are tricky to do in pure analog without too much variation, and power-on reset is surprisingly tricky to dowellalso.Alternatively, you could charge a low-leakage capacitor through a resistor and use two comparators to find when the signal is between two thresholds. The trick is to make sure it fully discharges when you power down, and to make sure it doesn't discharge through the comparators (they must have a very high input impedance).

author: Dajgoro
author_rank: Frequent Contributor
timestamp: August 13, 2013, 03:57:02 pm
content: What about a binary counter and then a comparator to trigger a t bistable so that you build a sorta simple state machine?

author: kripton2035
author_rank: Super Contributor
timestamp: August 13, 2013, 04:12:00 pm
content: one ne555 as master clock, at 1Hzthen a cd4017 as a "state machine" and the 10 outputs with some logic to turn on and off the relaybut yes it would be far easier with small mc !

author: Dave
author_rank: Super Contributor
timestamp: August 13, 2013, 04:20:01 pm
content: I don't see why you would need to solve this without a microcontroller. You could easily do this with a small micro like the ATtiny4. It doesn't get much smaller than that.

author: Crazy Ape
author_rank: Regular Contributor
timestamp: August 13, 2013, 04:30:27 pm
content: Take a look at this, but without the output tied back to the input (otherwise it's an oscillator).Change the RC components for the delay times you need.http://circuit-diagram.hqew.net/Phase$2dShift-Oscillator-with-Inverter-Gates_4801.html

author: Crazy Ape
author_rank: Regular Contributor
timestamp: August 13, 2013, 04:31:20 pm
content: You'll need to cut'n'paste the link in my last post, the forum didn't like it.

author: hlavac
author_rank: Frequent Contributor
timestamp: August 13, 2013, 04:39:19 pm
content: Use 556. One 555 to provide power up delay, other to make the 2s pulse.

author: mariush
author_rank: Super Contributor
timestamp: August 13, 2013, 05:31:59 pm
content: By the time you add the resistors and capacitors to the 556 you get 2-3 times more wasted space compared with a tiny pic10 or attiny in soic or other small format.

author: hlavac
author_rank: Frequent Contributor
timestamp: August 13, 2013, 05:57:53 pm
content: Yes but if he does not want to learn programming microcontrollers and/or does not have the programming hardware required to do so it does not matterIt will still be huge with that relay anyway...

author: SeanB
author_rank: Super Contributor
timestamp: August 13, 2013, 06:23:42 pm
content: I did that a long time ago using only one CD4066 analogue switch, even had a spare one left. First one was a simple on delay, driving the second as a monostable to drive the third which was emulating a keypress. I did this with a clock radio that has a CD player, but which would not turn the CD to play with the onboard timer, though it did turn it on. This small circuit was built on a small piece of veroboard and wired up behind the player front panel to emulate pressing play after 5 seconds of power on.Was arranged with a RC across the power rails driving the first switch input, and when it reached threshold and turned on it applied power to a second RC that generated the pulse driving the third switch. I had a 10uF capacitor and a 1k resistor across the power rail so it turned off fast and properly on power off.

author: TerminalJack505
author_rank: Super Contributor
timestamp: August 13, 2013, 06:38:11 pm
content: Another couple of options: 74HC123 or even a 74HC14 (with some RC networks.)

author: RoadRunner
author_rank: Frequent Contributor
timestamp: August 13, 2013, 07:21:58 pm
content: i guess CD4060 can also be used for such purpose .

author: TerminalJack505
author_rank: Super Contributor
timestamp: August 13, 2013, 07:54:45 pm
content: Just to annoy the "just use a MCU" crowd, here's a circuit that uses either a 74HC14 or 40106 IC (hex Schmitt trigger.) An additional filter at the second stage (or on the output) might be necessary since a quick pulse might shoot through at power-up.The first diode and the 470R resistor are to protect the IC from C1when the circuit is powered down. The diode parallel to R2prevents the gate from being pulled below ground through C2.An active high output and an active low output are provided.

author: Zero999
author_rank: Super Contributor
timestamp: August 13, 2013, 08:48:02 pm
content: Each to their own.We don't know the power supply voltage or relay coil resistance. A SE556 only needs a couple of resistors and capacitors, can drive a 200mA relay directly and work from 4.5 to 18V.

author: dr.diesel
author_rank: Super Contributor
timestamp: August 13, 2013, 08:55:22 pm
content: Quote from: c4757p on August 13, 2013, 03:52:57 pmThese cost ~ $0.60 and are as easy as Sunday morning, you can't go wrong.

author: MasterOfNone
author_rank: Regular Contributor
timestamp: August 13, 2013, 11:34:14 pm
content: Maybe something to try on your breadboard if you have a few components laying around.Make R1xC1 smaller than R2xC2.At start Q2 is on, and Q1 off, so C1 charges causing Q1 to switch on (powering the Relay), later C2 charges switching off Q2 which switching off the Relay.Edit: changed ‘R2xC3’ to ‘R2xC2’.

author: Stonent
author_rank: Super Contributor
timestamp: August 14, 2013, 01:16:39 am
content: I had to ideas this morning on this, both are more analog in nature.1. Use a PTC in parallel with the coil on the relay. It operates like a shunt for a few seconds and then breaks contact which allows the relay coil to energize. Have a low rated circuit breaker in series with the coil. The reset button is your button to start the process.2. Clock motors and micro switches.

author: c4757p
author_rank: Super Contributor
timestamp: August 14, 2013, 01:21:01 am
content: Quote from: Stonent on August 14, 2013, 01:16:39 amOoh, old-school!

author: Stonent
author_rank: Super Contributor
timestamp: August 14, 2013, 01:30:19 am
content: Quote from: c4757p on August 14, 2013, 01:21:01 amYeah, I had another idea about using a NOR gate and a MOSFET but it got a bit complicated. Or more so than I can picture at once.

author: TerminalJack505
author_rank: Super Contributor
timestamp: August 14, 2013, 04:23:00 am
content: Quote from: Hero999 on August 13, 2013, 08:48:02 pmYes, the 556 is probably a better solution to what I mentioned (74HC14, 40106 or 74HC123.) Like you say, it has a wider voltage range than the 74HC ICs and a more robust output.It also has the advantage that the constant factor use for the timing is higher than any of those ICs. It is probably twice as high. This means the timing capacitors can be half the size.

author: mortos360
author_rank: Regular Contributor
timestamp: August 14, 2013, 10:30:54 am
content: Thanks for all yours answers and reminding me again how little I know about electronicsI am not sure what I expected when I asked this question, maybe some other little IC that doesnt need programming to do the job.. but I guess the simplest solution would be a attiny and make a little standalone arduino.I would love to go away form arduino but its all I know atm and as much I would like to learn general MC programming... its just not as easy as taking another arduino...Anyway.. thanks for all your answers.. I cant say that I understood all of them, but I am sure I will try some of them just for the learning!!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 14, 2013, 11:22:46 am
content: Linear do some simple chips for this type of thing, but last time I looked they cost more than a PIC10F200http://www.linear.com/products/timerblox

author: Excavatoree
author_rank: Frequent Contributor
timestamp: August 14, 2013, 12:39:33 pm
content: With the gooligum.com series on basic PICS and a 10F200 you won't have any trouble, and it shouldn't take long to learn. It would make a good first "non arduino" programming exercise - in my opinion. For experienced folks - would that be a good learning path? I ask because that's where I am, now. I've got my "traffic light" running with a PIC 10F2xx and my Pickit.