2 sec pulse converted to 1 sec pulse

[rocs78]

Hi people!

I have a newbie question here. I have a timer circuit (taken from a wall clock) and when powder this circuit gives a high voltage output (+8v) every 2 secs. I am feeding this input into another project I am building and need to know if there is a simple way (or an IC) that will allow me to convert this 2 sec pulse into a 1 sec pulse?

Basically I need the +8v to be sent every second rather then every 2 seconds? Any easy ways to do this?

Cheers!

 

[ericgibbs]

Hi people!

I have a newbie question here. I have a timer circuit (taken from a wall clock) and when powder this circuit gives a high voltage output (+8v) every 2 secs. I am feeding this input into another project I am building and need to know if there is a simple way (or an IC) that will allow me to convert this 2 sec pulse into a 1 sec pulse?

Basically I need the +8v to be sent every second rather then every 2 seconds? Any easy ways to do this?

Cheers!

hi,
You could use a 555 timers as a Monostables, with time as 1Sec delay triggering a second 555 mono.

2Sec pulse in, 1Sec pulse out.

 

[Torben]

Hi rocs,

Welcome to the forum! I have to head to bed so I don't have time to work the whole thing out, but I think what I would try would be to invert the output of a missing pulse detector set to look for 2 sec pulses and use that to trigger a 555 astable circuit to generate a 1 sec pulse train whenever a 2 sec pulse train was present on the input.

You could probably do this using fewer parts using a microcontroller but I think a handful of resistors, capacitors, and a couple of 555s (or one 556) should do the job.

If no-one else has any better ideas I'll see if I can't take a look at this over the weekend.


Torben

 

[Mikebits]

If you don't care about duty cycle you could use a XOR, delay and a D FF . This would make a narrow pulse but for edge triggered apps it is ok. Google clock doubler.

 

[rocs78]

Thanks for the tip guys! I think I have the problem sorted now!

The 555 timer base seems to be easiest and fastest way of doing what I need! I am still kicking myself for not thinking of that earlier!!

Thanks for all the help!

Cheers!

 

[eblc1388]

Two 555s are suggested.

Can one achieve the same result by configure a single 555 to oscillate at 1Hz and then applying the two second pulse from the timer to sync the 555?

 

[KMoffett]

rocs78,

Not sure where you are taking the pulses from on your clock, but if it's like the small modules in the 1.5v battery operated clocks there are two outputs. Each output briefly pulses one end of the clock motor coil, in an alternating fashion at 2 second intervals, but 180 degrees out out of phase (first schematic). You can combine these two pulses with a simple diode-OR circuit, so you have an output of one pulse per second. (second schematic).

This may not be the case for your clock, but it works for the 1.5v ones.

Ken

 

[rocs78]

KMoffett.

You are a genius! I wasn't using a clock circuit as such, BUT your idea of using a clock circuit from a wall clock is brilliant!!! This will save me heaps of time (and they are small units). I have several old cheap clocks lying around that I will start stripping My circuit runs at 9V so I will just use a resistor to drop the voltage to some the clock circuit can handle (I think they max at about 3v)

Thanks for all the help!

 

[KMoffett]

This is a little circuit that I used to power the 1.5v clock from a 12v supply. R1, D1/D2 and C1 form a 1.4v shunt regulator. R1 and D3 are just for reverse polarity protection. R1's value is not critical.

As an aside...I wondered how accurate these clocks were compared to the line operated clocks (NIST traceable over long periods of time). Because I never have to reset my battery operated clocks, I was pretty confident, but to check I set up two electronic counters. One driven off the 60Hz line through a divide-by-60 circuit, and the other though my diode-OR circuit from the gutted clock, for two 1-PPS signals, The gutted clock ran slight off, by a few thousand counts over a couple of days. ??? Though I haven't gone back and tested it, I think gutting the clock circuit, removing the motor coil, and cutting away some of the metal frame may have shifted the crystal oscillator circuit frequency by a slight change in capacitance. I need to do this again, but without any change to the clock.

Ken

 

[Hero999]

Don't just use a resistor on its own, the voltage will be unpedictable and vare as the load changes, use a couple of diodes and a resistor to give you 1.2V which should be enought to drive your clock module.

 

[KMoffett]

Don't just use a resistor on its own, the voltage will be unpedictable and vare as the load changes, use a couple of diodes and a resistor to give you 1.2V which should be enought to drive your clock module.

Hero,
Isn't that what my schematic shows???
Ken

Added: Sorry Hero, didn't realize who you were replying to.