Hello,
I'm trying to build a meeting timer for my college fraternity. It's been about 6 years since I took my electronics classes and I was looking for some help.
I would like to have a final product of a box with three lights (Green, Yellow, Red), two buttons (Start, reset), some way to set the time (thumb-wheel switch), and possibly a buzzer (with a switch to kill it).
The way that I would like it to work is as follows:
Say the thumb-wheel is set for 5-min.
When the start button is pressed, the green light lights up.
After 4 minutes, the green light shuts off and the yellow light turns on. (and possibly a very short burst on the buzzer).
When the 5 minutes is up, the red light comes on (and optionally, the buzzer turns on).
The reset button is pushed an then all lights/buzzers are off awaiting next start press.
I was thinking of using two BCD-countdown timer chips and some 74xx logic to pull the 1 min left and 0 readings. Like I said, I havn't done any electronics work for about 6 years (I'm a power systems engineer). Does anyone have a better way? I don't have access to any type of PIC writing equipment, so that is out of the picture. I've thought about just using electromechanical relays, but want a smaller package that can run on batteries. If someone has a really simple circuit, I would appreciate it.
If this has already been discussed, I apoligize, I searched for about 20 minutes before posting this.
I'm trying to build a meeting timer for my college fraternity. It's been about 6 years since I took my electronics classes and I was looking for some help.
I would like to have a final product of a box with three lights (Green, Yellow, Red), two buttons (Start, reset), some way to set the time (thumb-wheel switch), and possibly a buzzer (with a switch to kill it).
The way that I would like it to work is as follows:
Say the thumb-wheel is set for 5-min.
When the start button is pressed, the green light lights up.
After 4 minutes, the green light shuts off and the yellow light turns on. (and possibly a very short burst on the buzzer).
When the 5 minutes is up, the red light comes on (and optionally, the buzzer turns on).
The reset button is pushed an then all lights/buzzers are off awaiting next start press.
I was thinking of using two BCD-countdown timer chips and some 74xx logic to pull the 1 min left and 0 readings. Like I said, I havn't done any electronics work for about 6 years (I'm a power systems engineer). Does anyone have a better way? I don't have access to any type of PIC writing equipment, so that is out of the picture. I've thought about just using electromechanical relays, but want a smaller package that can run on batteries. If someone has a really simple circuit, I would appreciate it.
If this has already been discussed, I apoligize, I searched for about 20 minutes before posting this.