Hello, I am attempting to build a timer/logic circuit and need some assistance. It has been close to 30 years since I used to do this type of work and now have a need to build something I thought would be simple. I found this forum and thought I might be able to get some assistance here.
I have attached to pdf documents that attempt to help describe my need. 1 document is a over simplified block diagram, and the 2nd document is a timing chart with 3 eample shown.
Desription of circuit:
I have 2 inputs that are fed from a device that uses npn transistors for outputs sinking to zero volts. The output needs to be high whenevr the 2 inputs are active, high. input A will always fire first.
Safety timer is a timer that will drive the output low in the case that inputs A and B stay high to long. the time on the safety timer needs to be adjustable between 5.-3 seconds
Skip Timer is an option selection that causes the output to follow the skip timer as long as the inputs A and B are high and the safety timer has not timed out. Skip timer needs to have adjustable high and low times between: .1 - 2 seconds.
The safety timer and skip timers must always start on the high cycle and be reset whenever the output goes low. This is to ensure that the timers always start from zero.
I have built a monostable timer for the safety timer, an astable time for the skip timer, a pnp transistor siwtch to convert the npn transistor input.
I am having a difficult time tying the cuicuit together and receiving the correct response or output.
Thanks in advance, I am open to any suggestion to this project.
Thanks, Dave
I have attached to pdf documents that attempt to help describe my need. 1 document is a over simplified block diagram, and the 2nd document is a timing chart with 3 eample shown.
Desription of circuit:
I have 2 inputs that are fed from a device that uses npn transistors for outputs sinking to zero volts. The output needs to be high whenevr the 2 inputs are active, high. input A will always fire first.
Safety timer is a timer that will drive the output low in the case that inputs A and B stay high to long. the time on the safety timer needs to be adjustable between 5.-3 seconds
Skip Timer is an option selection that causes the output to follow the skip timer as long as the inputs A and B are high and the safety timer has not timed out. Skip timer needs to have adjustable high and low times between: .1 - 2 seconds.
The safety timer and skip timers must always start on the high cycle and be reset whenever the output goes low. This is to ensure that the timers always start from zero.
I have built a monostable timer for the safety timer, an astable time for the skip timer, a pnp transistor siwtch to convert the npn transistor input.
I am having a difficult time tying the cuicuit together and receiving the correct response or output.
Thanks in advance, I am open to any suggestion to this project.
Thanks, Dave
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