timer

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danielsmusic

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i need to make a timer for a robot im making.
if i press a button it will turn a led on for the exact same time for when i pressed the button, when i press another button the led will turn on i cannot use pic chips.

i hope i worded this one right .

thanks
 
You press a button to light the LED or you press another button to light the LED.
Why use two buttons to do the same thing? :?: :?:
What activates a timer? :?: :?:
 
i hold a button in.
i let go.
i press a other button.
a led comes on for exactly the same time i pressed the first button
 
I suggest that you charge a capacitor from a constanr current source while the first button is pressed.

Then when the second button is pressed, turn the LED on and discharge the cap with a negative current source of the same amplitude. Use a voltage comparitor to detect when the cap voltage has fallen to its initial value - which will take about the same time as the charging time. When the comparitor detects the initial voltage, it turns the LED off.

Len
 
I have thought about your timer.

A counter solution would be simpler. What voltage do you want to operate it from? What is the maximum time you want to hold the button for?

Do you want to hold the second button while the LED is on, ie. hold the button until the LED goes out? Or do you want it to be a momentry action only?

If you answer these questions, I'll post a suggestion for you tomorrow.

Len
 
hold a button in.
i let go.
i press a other button.
a led comes on for exactly the same time i pressed the first button
Click to expand...

the second button is a microswich it does'nt matter if i press it in to turn on or let go.

the only time the led should turn on is when i have let go or pressed the second button :lol:
 
Hi

I have an idea for you but i don't no if it's usefull in your situation.
anyway i suggect you to use a conter (such az 74160) to count upward while you are holding first button then count downward while you hold secend botten.
LED whil be on until you reach 0000.
using faster pulser az clock pulse will increase the timer precise.
 
 
Here is a revised circuit.

I forgot to include a low pass filter on Co to prevent decoding spikes from resetting the flip flop.

Len
 

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danielsmusic said:
thank! its not quite what i want but it will do.
Click to expand...

I asked you to specify what you wanted, but your answer

danielsmusic said:
the second button is a microswich it does'nt matter if i press it in to turn on or let go.

the only time the led should turn on is when i have let go or pressed the second button
Click to expand...

is vague and ambiguous.

If you want people to do designs for you, you must specify your requirement clearly.

Len
 
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