Author Topic: What type of circuit will output 5V when a threshold is crossed?  (Read 1799 times)

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Offline MerlysysTopic starter

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Input peak is unknown, 0~20V
Output is to be 5V when the threshold is crossed. Threshold should be adjustable.
Propagation delays, accuracy not important.
Output goes to logic analyzer(LA) (since LA inputs must be <6V). Circuit is for preliminary investigation of commercially made equipment, laser printer scanner module in this case. I want to see where in the circuit changes occur so they can be examined more closely by oscilloscope.

Is there an IC that will make several of these circuits at minimum size/cost? Best if 8+ points in the circuit can be examined by the LA simultaneously.

Schmitt triggers is probably where I should start at, are there other types of IC based circuits? I looked into transistor based STs as I got lots of transistors lying around but they need several supporting components.

Perhaps there is a completely different approach to this that I am missing.



 

Offline madires

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Re: What type of circuit will output 5V when a threshold is crossed?
« Reply #1 on: March 03, 2014, 02:50:51 pm »
I think you're looking for a comparator like LM339.
 

Offline deth502

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Re: What type of circuit will output 5V when a threshold is crossed?
« Reply #2 on: March 03, 2014, 06:13:35 pm »
yup, comparator.
 

Offline Pillager

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Re: What type of circuit will output 5V when a threshold is crossed?
« Reply #3 on: March 03, 2014, 06:45:59 pm »
I used a 7805 once for turning a 24V-high-signal to a 5V-high-signal. Been working for 3 years.
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Tom
 

Offline w2aew

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Re: What type of circuit will output 5V when a threshold is crossed?
« Reply #4 on: March 04, 2014, 12:37:11 am »
I think you're looking for a comparator like LM339.

Ditto on the LM339. With the open collector output, it's easy to get any high level you need.
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