5 second reset?

555 oneshot

A time delay relay would also work, but they are not inexpensive. Might be overkill for your application, but ready off-the-shelf. Many are DIN-rail mountable, etc.. Search Digikey for Relay, time-delay

A time delay relay would also work, but they are not inexpensive. Might be overkill for your application, but ready off-the-shelf. Many are DIN-rail mountable, etc.. Search Digikey for Relay, time-delay

Might suffer contact bounce - an electronic solution would be better.

Seems like someone must sell a clock chip/package that puts out one pulse per second? Then you just have to count to 300. 'course I don't know of any such device.

George H.

Is there some reason that the PLC logic can't be modified to accommodate your needs?

(...)

The electric company provides pretty accurate 60 Hz for that divide - by - 300 circuit.

It'll cost you a small transformer, a couple diodes and a resistor.

--Winston

You could use a CD4060. This is a schematic for a similar project:

The schematic shows some interesting tricks: The reset of the CD4060 is generated by C1 and R1 (of course, this works only, if the power supply doesn't start very soft, a POR chip would be more safe). Then the counter stops, when it reachs Q9, because this is fed back to the oscillator input, decoupled by D7 (you can ignore the other Q outputs for your problem). So you could adjust C4, R5 and R7 (I would use a much lower resistance for R7, some 100k) to generate some kHz and then try out which output gets high after 5 seconds and use this for your reset and wire it with a diode to pin

1. If you don't need a very accurate 5 s delay, you don't need a crystal, but use a ceramic capacitor for C4, electrolytics can dry out after some years, which results in delay time change.

Of course, I would use a PIC microcontroller, which has an integrated oscillator and integrated POR, so no additional parts are needed (except one power decoupling capacitor). A simplified version of this project should solve your problem:

--
Frank Buss, fb@frank-buss.de
http://www.frank-buss.de, http://www.it4-systems.de

Dont know yet. The manufacturer recommends so for this 15+ years old TNS PLC.

Sonnich

Let me just ask - the schematic is not that clear from the 4060 datasheet - that pin 7, Q4, will toggle every 16 pulses?

Binary Counters, yes, but I am not sure what Ripple Carry is?

Sonnich

Seems like someone must sell a clock chip/package that puts out one pulse per second? Then you just have to count to 300. 'course I don't know of any such device.

Rip the PCB out of a quartz analogue travel clock and use a couple of forward biased diodes and a dropper resistor for its supply.

Let me just ask - the schematic is not that clear from the 4060 datasheet - that pin 7, Q4, will toggle every 16 pulses?

Binary Counters, yes, but I am not sure what Ripple Carry is?

********

Ripple carry is where divider Q output is fed to the CLK of the next divider so the pulses "ripple" down the chain.

As opposed to synchronous counters where all the CLK inputs are in parallel and all the dividers change state (or not) simultaneously on the rising (or falling) edge of CLK.

--
The 4060 is a 14 stage binary ripple counter with an on-board
oscillator circuit.

It works by progressively dividing the input clock by succesively
higher powers of 2 up to a maximum of 16383 clocks, when all of its Q
outputs will be high.  

Then, on the 16384th clock, it'll reset and all the outputs will go
low, starting a new count cycle.

I didn't think of it before, but you can probably also use a line stretcher for this. These devices are commonly used in residential / commercial security alarms to enlongate the signals from fast-acting sensors (like vibration sensors). If the sensors react too quickly, the alarm panel might "miss" the event entirely, hence the need to stretch the signal. They are cheap. Under $10 wholesale.

Something like this one:

pdf ....though this particular model might not be the best choice?

I've seen some that have adjustable stretch times. Google pulse stretcher.

Or of course, the designs offered here will certainly work too if you want to make your own board, etc... If I were going this route, I'd use a PIC, or one of those NXP 8-pin

8051 types. LPC901? Good luck.

-mpm

I

divide

Reset for PLC is so not like reset for uC.

--
Oops...

Two 4060's won't work because the LSBs aren't pinned out, but a 4060
and a 4024 will.