Event Driven Timer with rotary switch selection

[Randallman]

Looking for a selectable 1-10 event counter with a selectable time of 1 4 8 and 16 hours.

So basically a rotary switch with 10 positions to select the count and a rotary switch with 4 positions to select the time between events.

When the selected count is done then set an output pulse to and NPN open collector transistor rated for 100mA for 1 second, then start selected timer 1 of 4 positions 1, 4, 8, or 16 hours when timer is done reset counter and start again.

I am looking to use either common timers like the 555 556 or other timer chips that are long delay would like to use common counter chips like the 4017, no digital displays required. Just keep it simple with two rotary selectors.

If anyone has such a circuit or can direct me to someone like an electronics consultant it would be appreciated.

 

[srizbf]

for such long time counting and switching sequences , a microcontroller with minimal pin count is the choice.

the input rotary switch can be of general type or bcd type.

 

[d123]

Hi,

Page 10 of the app note has a suitable/similar schematic. The n8281 has an equivalent part NTE 74177, not sure but look like pretty old ICs, still available to buy though.

The obsolete 558 (open collector output) also has a long time delay schematic on the NXP datasheet, page 4, link below.

Maybe you could look at the CD4060 and perhaps cascade two if necessary to get 10 outputs (and cascade to slow down even more if one IC can't manage a 16 hour pulse). If that can work for you, then no need for the 555 - hopefully less parts! Also, a flip-flop IC can be placed on an output to halve frequency if need be.

**broken link removed**

The accuracy may be a bit non-ideal over such long time delays, perhaps, so helpful may be reviewing ideal passive components for this type of circuit, also described in the 555 app note.

Using a CD4060 or two (or TTL equivalent part) means you can use a crystal oscillator, which would improve timing accuracy/repeatability very much.

I think you could use a single pole 4-way rotary switch, and probably even a cheap one if you only need four outputs and contact resistance is irrelevant to the application.

 

[Randallman]

Hi,

Page 10 of the app note has a suitable/similar schematic. The n8281 has an equivalent part NTE 74177, not sure but look like pretty old ICs, still available to buy though.

The obsolete 558 (open collector output) also has a long time delay schematic on the NXP datasheet, page 4, link below.

Maybe you could look at the CD4060 and perhaps cascade two if necessary to get 10 outputs (and cascade to slow down even more if one IC can't manage a 16 hour pulse). If that can work for you, then no need for the 555 - hopefully less parts! Also, a flip-flop IC can be placed on an output to halve frequency if need be.

**broken link removed**

The accuracy may be a bit non-ideal over such long time delays, perhaps, so helpful may be reviewing ideal passive components for this type of circuit, also described in the 555 app note.

Using a CD4060 or two (or TTL equivalent part) means you can use a crystal oscillator, which would improve timing accuracy/repeatability very much.

I think you could use a single pole 4-way rotary switch, and probably even a cheap one if you only need four outputs and contact resistance is irrelevant to the application.

Hello I like your suggestions, I would like to not use a microcontroller for this application, please see my attached schematic of what this circuit may look like using a 4017 and TBD long duration timer chip. Upon power up the 4017 is reset and the timer is reset. when the selected count is reached then the timer start is initiated, at the end of the timer duration the timer out goes high.

 

[d123]

Hi,

What's that "Timer Chip TBD", please? Can you tell me a part name (as I' d like to have a read of the datasheet)? What drives the count switch in the schematic? It's an interesting circuit, I'd like to know more about it, thanks.

 

[Randallman]

Hi d123,

Thanks for your interest in my circuit, the TBD is (to be determined) I found an inexpensive long time duration chip used in a 24 hour timer circuit I found online it is a CD4060, my plan is to use the 4 position selector to select the range between pins 15, 1, 2 and 3. the chip is available at Digikey in a 16 pin dip for 52 cents, the count switch is actually going to be a thru beam sensor. The time duration s are not critical plus or minus 10 to 15 minuets is not a problem. I need to add a one shot circuit from the count selector switch ti start the timer as the count out stays on (high state). See attached.

Thanks again any more suggestions are welcome.

 

[BradtheRad]

I agree the 4060 is a good choice. I used a 4020 (a cousin, similar but lacks oscillator) to construct a similar long-duration timer.

 

[d123]

Hi,

Thanks... dohhhh: TBD, I thought it meant some specific kind of IC . Great, the 4060 is a great analog tool. I deduce you're in the UK? ...Maplin Electronics gives it away!

Do you mean a one-shot for the part of the schematic that says "count switch" or the one that has the 4060 and says reset? You can do that with a 555 (and probably a few more required components, I'm guessing). If something goes low at the end of the timing period it can trigger a 555 to do a quick high output pulse - I really recommend browsing Rob Paisley's 555 circuits if you're not familiar with his website, I learnt a lot of useful timer circuits from his web.

**broken link removed**