steve_locher25
- Mar 16, 2010
- 5
- Joined
- Mar 16, 2010
- Messages
- 5
I'm trying to build a 9 digit LED 7 seg display timer that can measure uS (microseconds).
I would love to have it measure nano seconds, but looking at the data books, it seems my idea will not work for nano because of rise / fall times, max freq of 555 timer, propagation delay etc etc.
But, there are still some projects I'm working on where it would be nice to be able to measure just how long a pulse width is from a one shot for example, and so I've decided to try to build it to measure at least 1 microsecond.
Basically, since I still don't own an oscilloscope, I'm building a somewhat precision timer.
On hand I have a NE555P, but, not sure of it's max freq (100KHz?? and if so, would not be fast enough?? for microseconds I need 1 MHz, clock speed, right?)
I've already hooked up a 3 digit LED 7 seg display, and after tuning it with a 1Meg pot, I had it measuring .01 seconds like a charm. (was running MC14553BCP into a MST6911C at 5Vdc)
Found a TLC555CP that is rated at 2.1 MHz maximum, thinking about firing that up after I add the 2nd and 3rd set of displays. (3 sets of 3 digits when finished)
For tuning, I'm using an LCD display kitchen timer, and then adjusting the pot, after so many minutes go by, a little faster here, little slower here, until the seconds on both are incrementing at the same time. I think when I get into the millisecond range, I'll have to add another smaller pot to fine tune it, etc.
So, my questions are:
1) am I wasting my time because even after I spend all that time tweaking it, it might not be the same the next time I use it (drift? temperature changes? etc.)
2) should I try a crytal instead of a 555 timer?
your thoughts?
Steve
I would love to have it measure nano seconds, but looking at the data books, it seems my idea will not work for nano because of rise / fall times, max freq of 555 timer, propagation delay etc etc.
But, there are still some projects I'm working on where it would be nice to be able to measure just how long a pulse width is from a one shot for example, and so I've decided to try to build it to measure at least 1 microsecond.
Basically, since I still don't own an oscilloscope, I'm building a somewhat precision timer.
On hand I have a NE555P, but, not sure of it's max freq (100KHz?? and if so, would not be fast enough?? for microseconds I need 1 MHz, clock speed, right?)
I've already hooked up a 3 digit LED 7 seg display, and after tuning it with a 1Meg pot, I had it measuring .01 seconds like a charm. (was running MC14553BCP into a MST6911C at 5Vdc)
Found a TLC555CP that is rated at 2.1 MHz maximum, thinking about firing that up after I add the 2nd and 3rd set of displays. (3 sets of 3 digits when finished)
For tuning, I'm using an LCD display kitchen timer, and then adjusting the pot, after so many minutes go by, a little faster here, little slower here, until the seconds on both are incrementing at the same time. I think when I get into the millisecond range, I'll have to add another smaller pot to fine tune it, etc.
So, my questions are:
1) am I wasting my time because even after I spend all that time tweaking it, it might not be the same the next time I use it (drift? temperature changes? etc.)
2) should I try a crytal instead of a 555 timer?
your thoughts?
Steve