Create an UP-DOWN pulse from a single UP to DOWN signal

[robertbarron]

Hi
I am just a hobbyist using electronics in my retirement.

I have recently made a light chaser and then made it move up the line of 10 leds and then back down etc etc. I used a 4069 inverter circuit to produce the clock pulses followed by a 4510 U/D counter feeding a 40218 1 to 10 decoder. The 1st and 10th outputs from the decoder fed a 4043 SET/RESET flip flop to get a signal to control the U/D of the 4510 counter. This all went well.

Now I tried to add a delay after each forward and backward light chase. This has run into serious problems based on the signal I take to initiate a delay (providing 2 seconds from a 555 monostable). The 555 requires a momentary high to low signal at its "trigger" pin 2 and this signal was taken from the working circuit BUT once the 555 received the signal and output its high signal, this high signal stayed because it stops not only the light chase but also locks the signal I used to trigger the 555.

The trigger pulse has to be from high to low to high and shorter than the required 2 second output. If the trigger signal remains low, the 555 signal stays high (no timing allowed until the trigger signal goes back to high).This puts me into a vicious circle.

Please help me if possible. I need to get an up - down signal using a high to low signal. If this is possible, it will provide the 2 second delay and then permit the clock signal to continue and thereby remove the trigger signal which locks during the delay time.

 

[AnalogKid]

Really need to see your schematic to sort out the details, but this should not be too difficult to solve. One thought is to use stages of another 4069, or 40106 or 4093 to make the delay signal. You'll have much more control over logic polarities and you won't have to deal with the 555's personality issues.

Do you want all of the LEDs to be dark during the delay, or do you want the circuit to sit on the end LED for the extra delay period before reversing?

ak

 

[Harald Kapp]

The trigger pulse has to be from high to low to high and shorter than the required 2 second output.

Use a capacitor to couple the signal into the 555's trigger input as shown e.g. here. This will create a trigger from the edge of the input signal only.

In case your issue isn't solved by this simple measure, @AnalogKid is right in asking for a schematic.

 

[dorke]

1. As far as I know, there is no such part 40218 you, probably mean 4028.

2. The way you implement this is very cumbersome!
a single 4017 (10bit ring counter) can replace the 4510+4028.

3. For much more freedom with the light chasing patterns use a universal shift register.
You can use the 4bits CD40194, it can be cascaded to any number of bits you need.

4. Do post the diagram of what you have so far.

 

[robertbarron]

Please help me if possible. I need to get a fast up down signal using a high to low signal. If this is possible, it will provide the 2 second delay and then permit the clock signal to continue and thereby remove the trigger signal which locks during the delay time.

Hi
I am just a hobbyist using electronics in my retirement.

I have recently made a light chaser and then made it move up the line of 10 leds and then back down etc etc. I used a 4069 inverter circuit to produce the clock pulses followed by a 4510 U/D counter feeding a 4028 1 to 10 decoder. The 1st and 10th outputs from the decoder fed a 4043 SET/RESET flip flop to get a signal to control the U/D of the 4510 counter. This all went well.

Now I tried to add a delay after each forward and backward light chase. This has run into serious problems based on the signal I take to initiate a delay (providing 2 seconds from a 555 monostable). The 555 requires a momentary high to low signal at its "trigger" pin 2 and this signal was taken from the working circuit BUT once the 555 received the signal and output its high signal, this high signal stayed because it stops not only the light chase but also locks the signal I used to trigger the 555.

The trigger pulse has to be from high to low to high and shorter than the required 2 second output. If the trigger signal remains low, the 555 signal stays high (no timing allowed until the trigger signal goes back to high).This puts me into a vicious circle.

Please help me if possible. I need to get an up - down signal using a high to low signal. If this is possible, it will provide the 2 second delay and then permit the clock signal to continue and thereby remove the trigger signal which locks during the delay time.

 

[Harald Kapp]

Please supply a schematic of the signals and timing sequence intended, this will make it a lot easier to understand your idea.

 

[AnalogKid]

2. The way you implement this is very cumbersome! a single 4017 (10bit ring counter) can replace the 4510+4028.

The 4017 is not bidirectional.

ak

 

[dorke]

The 4017 is not bidirectional.

ak

Yes Kid,you are correct.