# CSS555C alternative, to create a long delay

Thread Starter

#### cgw94

Joined Jun 11, 2020
42
Was looking for a way to create a long delay, essentially I want to activate a circuit for a certain amount of time once or twice a day. I really dont have the space or budget to add a micro controller. I found some old articles talking about the CSS555C but it seems hard to find now. Is there a better solution on the market?

I also can't have it involve a giant RC circuit so I was hoping there was another chip out there. A little programming isnt a bad thing just want it to be as simple as possible.

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#### Audioguru again

Joined Oct 21, 2019
4,682
The CSS555 is a Cmos 555. I do not know why a standard readily available Cmos 555 cannot be used for your project like an ICM7555, LMC555 or TLC555. With a 20M resistor and a 10uF film capacitor its timeout is almost 200 seconds.
If an electrolytic capacitor is used then its leakage current might cause no timeout.
Cmos oscillator/counter ICs might still be available for a longer timeout.

#### KeithWalker

Joined Jul 10, 2017
2,354
The simplest way is to use a standard AC timer to power the 555 circuit that will turn on your device for the required time.

#### MisterBill2

Joined Jan 23, 2018
11,879
The cmos CD 4060 includes the potion of an RC oscillator and a long divider string. So it can provide much longer delays with a 1 minute or even ten second RC time interal. if 4095 seconds would be long enough. But the output ids only 5 volts so you may need a transistor such as the MPSA13 to provide a higher current capability. So look at the applications of the MC14060 or CD4060 IC.

#### Dodgydave

Joined Jun 22, 2012
10,303
Easiest option is a digital plug in timer, these use a relay which you can modify and use the contacts to switch on your item on .

#### upand_at_them

Joined May 15, 2010
896
A space limit? An 8-pin microcontroller is no bigger than an 8-pin 555 timer. And about the same cost.

#### Audioguru again

Joined Oct 21, 2019
4,682
For long timeouts, a CD4536 and a CD4541 oscillator/counter/timer ICs are also available. Digikey and others have lots in stock.

#### AnalogKid

Joined Aug 1, 2013
10,054
AND - CD4521.

Also, Both Linear Tech and Maxim make silicon oscillators, and might have one with a long divider built in.

ak

#### djsfantasi

Joined Apr 11, 2010
8,323
A space limit? An 8-pin microcontroller is no bigger than an 8-pin 555 timer. And about the same cost.
Add a TO92 N channel MOSFET (2N7000) and two resistors, and you can switch just about anything.

ak

#### upand_at_them

Joined May 15, 2010
896
As AnalogKid said, you can make the delay as long as you want, it's just incrementing a variable. My experience with the 1% accurate PIC's is that they're even better than that. But still, 1% is 14.4 minutes per day. Keep that in mind. Adding a crystal will get you much better accuracy if you need it.

#### djsfantasi

Joined Apr 11, 2010
8,323
Could i get a long delay with just a simple controller chip like that?
You can easily get long delays with an 8 pin MCU. You can also get multiple events based on the clock. Or have multiple inputs... up to five... to control your output. Or up to six outputs based on individual times. With code, the tiny MCU can give you lots of flexibility.

#### MisterBill2

Joined Jan 23, 2018
11,879
With that 8 pin micro you also need a fair amount of extra I/O and if you need to change the time setting you need to get in and revise the software. Also you MUST have a regulated power supply, and lots of esd PROTECTION. Even better, you need to be skilled enough to create the code, compile it, and down-load it. And if the device needs to be replaced just hope that it is still available. The CD4060 is made by several companies and has been around for many years and will still be around for many more.

#### djsfantasi

Joined Apr 11, 2010
8,323
With that 8 pin micro you also need a fair amount of extra I/O and if you need to change the time setting you need to get in and revise the software. Also you MUST have a regulated power supply, and lots of esd PROTECTION. Even better, you need to be skilled enough to create the code, compile it, and down-load it. And if the device needs to be replaced just hope that it is still available. The CD4060 is made by several companies and has been around for many years and will still be around for many more.
Good points. Except the extra IO. What do you mean by that?

#### MisterBill2

Joined Jan 23, 2018
11,879
Good points. Except the extra IO. What do you mean by that?
Extra I/O means thet the 8 pin IC is not able to drive any load beyond a logic IC. So it needs either a higher gain transistor or a buffer IC in order to do anything useful. . And it needs something external to tell it to start. And it probably needs a crystal and 2 capacitors for the clock oscillator.

Thread Starter

#### cgw94

Joined Jun 11, 2020
42
With that 8 pin micro you also need a fair amount of extra I/O and if you need to change the time setting you need to get in and revise the software. Also you MUST have a regulated power supply, and lots of esd PROTECTION. Even better, you need to be skilled enough to create the code, compile it, and down-load it. And if the device needs to be replaced just hope that it is still available. The CD4060 is made by several companies and has been around for many years and will still be around for many more.
Ah right ya forgot to mention the voltage supply is essentially coming from a pH probes voltage im boosting. (with batteries but very unstable)