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Need help toggling a 555 timer

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change1

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Hello, I am new on this forum. I am designing an electronic gift for my brother, and I need help to toggle a 555 timer for 100 ms with a rising edge. I need to toggle the 555 timer to start the next motor direction. I have thought of using a flip flop, but not sure if it will work? Any help would be appreciated. Thanks Below is the logic.

**broken link removed**
 
change1 said:
Hello, I am new on this forum. I am designing an electronic gift for my brother, and I need help to toggle a 555 timer for 100 ms with a rising edge. I need to toggle the 555 timer to start the next motor direction. I have thought of using a flip flop, but not sure if it will work? Any help would be appreciated. Thanks Below is the logic.

<snip>

Hi change,

Welcome to the forum.

Are you saying that all you need is to have the 555 trigger on a rising edge rather than a falling edge? If so, you could just put a transistor inverter in front of the 555's input. i.e. run your existing input to the base of an NPN via a 10k resistor (Rb), put the emitter to ground, and put the collector to +V via, say, a 1k resistor (Rc). Then take a line from the junction of the collector and Rc to the trigger input of the 555.

If you post the actual schematic (along with the voltages) you're having trouble with it will be easier to help.


Good luck,

Torben
 
Well here is a preliminary design. Here is a brief description of my design. I want to build a golfman with a DC motor. The golfman will swing a mini golf stick 225 degree at 9V (Slow Back Swing), and forward swing at 16 V (Fast Forward Swing) to hit a ping pong ball and stop at 405 degree. Then at 9V (Slow Back Swing) to the initial position.

1. Toggle the switch to trigger 555 timer #1
2. "Need help how to trigger the 555 timer #2 with the rising edge from timer
1"
3. Same as Timer #2. Timer #3 will be trigger with the rising edge from
timer #2.

This is just a preliminary design. Any help would be appreciated. Again, I am just a beginner at designing electronics. Thanks for your help.

**broken link removed**
 
OK, the general idea I was getting at is in my attachment. The output from the transistor I added is the inverse of whatever comes out of the first 555's output.


Torben
 

Attachments

  • golfman_with_inverter_cropped.png
    golfman_with_inverter_cropped.png
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Torben said:
OK, the general idea I was getting at is in my attachment. The output from the transistor I added is the inverse of whatever comes out of the first 555's output.


Torben

If the 555 #1's output is still high when #2 ends its timing cycle, then Torben's circuit wont work because the 555 needs to have its trigger input high in order to end its timing cycle.

You must add a series capacitor between the transistor's colector and the 555 #2 trigger (pin 2), and a resistor between the 555 #2 trigger (pin 2) and +V.

Try something like 10nF (= 0.01:mu:F) and 10K:eek:hm:
 
This the 555 Timer that I am planning to use. Pin 2 (Trigger) requires a short pulse high → low on the trigger starts the timer. Need to pull it low and then back up high to start timer 2 & 3 with the rising edge of timer 1 and 2.

**broken link removed**
 
change1 said:
This the 555 Timer that I am planning to use. Pin 2 (Trigger) requires a short pulse high → low on the trigger starts the timer. Need to pull it low and then back up high to start timer 2 & 3 with the rising edge of timer 1 and 2.

That's what I said....

To trigger on a falling edge, use a capacitor in series and resistor to +V to "shorten" the pulse.

To trigger on a rising edge, use Torben's transistor to invert the pulse and then the capacitor in series and resistor to +V to "shorten" the pulse.


Attmpting to draw in ASCII :D
Code:
                               o +V
                               |
                               /
                               \
                               /
                               \
                               /
                               \
                               |
              o-------||-------0---------> Trigger
From 555                                           (pin 2)
or transistor


Long pulse                                         Short pulse

____                _____                         ____     _____
    |              |                                  |  /
    |              |                                  |  |
    |              |                                  |  |
    |              |                                  |  /
     ______________                                    _
 
ecerfoglio said:
That's what I said....

To trigger on a falling edge, use a capacitor in series and resistor to +V to "shorten" the pulse.

To trigger on a rising edge, use Torben's transistor to invert the pulse and then the capacitor in series and resistor to +V to "shorten" the pulse.

Whoops, I left that possibility out. Thanks for pointing that out. :)


Torben
 
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