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A one time timer
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CopperCone:
If you dont mind paying more but you want easy and neat look at timerblox chips
Wimberleytech:

--- Quote from: Benta on May 30, 2018, 03:53:08 pm ---
The 4538 or 74HC4538 is a good choice whenever you need an edge triggered monostable multivibrator (MMV). Note the qualification: if you want a level triggered input (eg., when adding a certain extra time to a variable length input pulse) the 555 is better suited.

There are no tutorials on the 4538, simply because it is super-simple to use and the datasheet gives all the needed information. Choose a resistor and a capacitor for the desired pulse length and you're done.
As a bonus, you get two MMVs in the same package.


--- End quote ---
Cool, I have never used this part...learn something new every day here.  I noticed that the datasheet does warn about using large capacitors that can discharge into the chip on power down.  It tells how to solve this with an extra diode.
larsdenmark:

--- Quote from: Benta on May 30, 2018, 03:53:08 pm ---
--- Quote from: larsdenmark on May 30, 2018, 08:04:26 am ---@Benta - You are probably right about the CD4538. However, the world is short on tutorials on how to use the CD4538 or why one should use it.
Perhaps you could share a few (more) words about how and when to use the CD4538?

A quick search finds that the 555 is a lot cheaper than the CD4538 and the 555 is a lot easier to get.

--- End quote ---

The 4538 or 74HC4538 is a good choice whenever you need an edge triggered monostable multivibrator (MMV). Note the qualification: if you want a level triggered input (eg., when adding a certain extra time to a variable length input pulse) the 555 is better suited.

There are no tutorials on the 4538, simply because it is super-simple to use and the datasheet gives all the needed information. Choose a resistor and a capacitor for the desired pulse length and you're done.
As a bonus, you get two MMVs in the same package.

Concerning "a lot cheaper": Mouser shows 40 cents for the MC14538 and 30 cents for the NE555. Considering the monstrous capacitor you'll need for making a 5-minute delay with the 555, I'm certain that a 4538 solution will be much cheaper in the end.

Edit: the 7555 (CMOS version of the 555) costs 45 cents. And at such long time delays you're forced to use that version. So much for "cheaper".

--- End quote ---

Thank you for this information. I'm always willing to learn something about a new group of ICs. The datasheet for the ON Semiconductor version of the MC14538B has a nice little graph that I've attached. It shows that the MC14538B is only good for a pulse up to 10 s whereas  the MC14541B can do 5 minutes and the MC14536B can do 23 hours(1), which I guess is a lot more than the 555 can handle.

The datasheet for the NE555 says: "Timing From Microseconds to Hours" so it should do pulses of 5 minutes. Since I have a NE555 I made a small test with a 100 uF cap and a 2.7 MOhms resistor and it gives a pulse of slightly more than 5 minutes. I can buy the NE555 at TaydaElectronics for $0.13.
Benta:
The reason for the long times of the MC14541 and MC14536 is, that they're counters with built-in oscillator. Different story altogether.

The MC14538 will do 5 min. comfortably, but due to cap leakage currents not as precisely as up to 10 sec. But anyway, if you want precise timing, the oscillator/counter is the way to go.

The 555 claim of timing to "hours" is hard to believe. Finding a big cap with so little leakage current will be a major and expensive task and it will probably be the size of a whisky bottle, reducing the semiconductor cost to peanuts.

Who is Tayda Electronices? I only buy from authorized sources, which costs me a bit more, but saves me from a lot of grief.

larsdenmark:
It may be fun to try using a MC14536 (but a MCU may be easier to work with).

From what I can read both the 555 and MC14538  doesn't say anything about accuracy beyond 10 s. For a 1 s pulse the 555 has an accuracy of 1% whereas the MC14538  has an accuracy of 5%. Based on the original problem of just being able to have a pulse of 5 minutes I see no reason to not use a 555. However, there may be other very good reasons to use a MC14538 since it seems to support (as you write) a lot more options on triggering and input/putput handling.

Tayda is www.taydaelectronics.com . They are based in Thailand. I have used them for years and they have never disappointed me. Shipping to Denmark is 7 days.
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