Home DIY Electronics

Jack's Comment

Thu, 19 Sep 2024 19:16:00 +0100

How to disable the extended time during the duration of one cycle. If the duration is set to 1 minute, pressing the button several times during the cycle will continue the countdown without extending the time.

Wtorres's Comment

Fri, 28 Jun 2024 18:31:23 +0100

Translation!!

It's just what I need!! The only thing I had to add is a 100 ohm resistor in series to the potentiometer to protect the 555 in case the potentiometer reaches zero ohms

Wtorres's Comment

Fri, 28 Jun 2024 18:29:17 +0100

Es justo lo que necesito!! Lo único que tuve que agregar es una resistencia de 100 ohmios en serie al potenciómetro para proteger el 555 en caso de que el potenciómetro llegue a cero ohmios

Ravindran's Comment

Mon, 26 Feb 2024 14:41:19 +0000

I have assembled the circuit and working verywell. Tested upto 3 Hrs with 2200micro frad capacitor.
Used pnp transister Bc557 connected to out put of pin 3 with relay drive. I need one clarification. One end of the capacitor is connected to base of transistor Bc547. Pl clarify how discharge of capacitor is taking?

Ravindran's Comment

Mon, 26 Feb 2024 14:07:34 +0000

Ravindran's Comment

Mon, 26 Feb 2024 13:49:25 +0000

I have assembled the circuit and working verywell. Tested upto 3 Hrs. Used pnp transister Bc557 connected to out put of pin 3 with relay drive. I need one clarification. On end of the capacitor is connected to base of transistor Bc547. Pl clarify how discharge of capacitor is taking?

Paul's Comment

Wed, 02 Jun 2021 06:29:09 +0100

Agree with you but personally I would not use it for longer the 1 hour and only if the accuracy is not critical. But the 555 can be very use full. I sometimes will use them as a gate driver or just for its high current output. It is cheap and I always have a few in the bin.

Paul's Comment

Wed, 02 Jun 2021 06:14:22 +0100

If Current is not a problem and you are working from any supply above 5V with a added regulator to the attiny ext a LMC555 or 7555 would probably be much cheaper and will take much less time. May be for the same or smaller PCB depending on your PCB layout abilities.

Kamran's Comment

Thu, 07 Mar 2019 20:01:43 +0000

You can use the following calculation:
T=1.1 X R X C
R in Ohm, C in Farad, T in Sec
8 hours = 8 X 3600 sec = 28800 Sec
Do not use higher value of R (2.2MOhm and more)
The quality of the C is very important(Lower leakage, more accurate timing)

Darius's Comment

Thu, 25 Oct 2018 12:54:24 +0100

Why use 555 when you can use attiny? In sleep mode it runs on microamps. Timer interupt can wake it after specified time and put it back to sleep after logging is done.

venkat d's Comment

Tue, 23 Oct 2018 14:10:10 +0100

How to generate 22 hours Delay using 555 timers?

BambiB's Comment

Tue, 30 Jan 2018 19:58:48 +0000

Actually, there's a practical limit on 555 timing circuits caused by the leakage current of capacitors. An IDEAL capacitor will hold a charge forever, but a practical capacitor always has a leakage current. This is especially true in electrolytic capacitors (which are probably what you'll be using to achieve high capacitance values). I've read the leakage of an electrolytic can be in the range of several µA. If you use a 100K resistor to charge the capacitor, the charge current will be within an order of magnitude of the leakage current. Since all of this can vary by an order of magnitude within a reasonable temperature range, you may wind up with a "timer" that isn't accurate. And if the charge current is LESS than the leakage current, your device will never toggle.

The maximum reliable time interval for a 555 is probably less than 4 hours, depending on voltage, capacitor quality and value, and temperature. For extended accurate timing intervals, micro-controllers are the way to go, and for extreme intervals with reasonable accuracy (months with error ~ seconds) you might consider a dedicated timing circuit like a DS1307 or a micro-controller with an external crystal.

Harshal Raut's Comment

Tue, 05 Dec 2017 05:31:08 +0000

Hello,

Can I change the combination of both Resistor and Capacitor values to get delay of 8 hours? If yes, what might be the combinations of both ? Also, How to calculate the delay for this circuit? Is there any formula...

JM's Comment

Fri, 01 Dec 2017 07:34:18 +0000

How to generate a 1 minute pulse with 30 mins delay? Will it automatically repeat the cycle? Or it has to be reset manually.

Arularasan's Comment

Fri, 06 Oct 2017 05:49:43 +0100

How can I increase the time delay sir..

12 hours time cycle sir....how can I use the R1 value.. I waiting for your valuable response sir...share on e-mail sir..

BambiB's Comment

Tue, 19 Apr 2016 22:19:50 +0100

You'll want to use a small micro. 555s waste too much power for your application - and you're going to have to record the data anyway, so why not use a micro controller and write to a memory card that you can just plug in and read later?

The Atmel line offers processors with "pico power" operation. You can set a watchdog timer to wake up every 8 seconds or so. In this mode, the average power consumption is on the order of half a MICRO amp (about 1000 times less than your 555). When the watchdog timer times out, it jumps to an ISR that can do whatever you like. Some Atmel processors have on-board temperature sensors, and you can use that, or if you want to use an external sensor, that's easy enough to do. Read the data, write it to your memory card and go back to sleep. If you want one read every 10 minutes, you just decrement a counter which keeps track of the number of times the watchdog has timed out. So at 8 seconds, you just count down from about 75 and when you hit zero, take a reading. Of course, the processor will consume more power during the count/sense/write cycle, but it's still only on the order of a fraction of a mA, and it's only for a tiny fraction of a second.

The processors cost about a buck a pop and are available in 8-pin dip packages (which makes it really easy to mount them to a board).

Other manufacturers may have similar products. I just happen to be familiar with Atmel.

With an energy budget of 2000maH (assuming 3.3-5 volts), your logger should be able to record data for well over a year on a single battery.

Steve's Comment

Wed, 08 Jul 2015 23:14:09 +0100

Hi Chris,

Yes I'm sure that you can get a longer time delay from this circuit. I haven't tested it because it takes too long to do the test.

Try using a value of 820kO for RT or increase the value of the capacitor to 220uF and use 390kO for RT.

Both the above RC combinations should give you a delay of approximately 5 hours.

To generate a 1 second pulse after 5 hours you will need to follow the circuit with another 555 circuit configured to give you a 1 second pulse when the output from the first 555 changes state.

Hope this helps
Steve

Chris's Comment

Wed, 08 Jul 2015 22:23:27 +0100

Hi,
Thanks for your guide. I'm looking for a long timer with a 1 second pulse at the end to start a washing machine. Is it likely that I could extend the delay to around 4-5 hours using your method above?
Thanks.