# Testing Signals Above Threshold Voltage Non-Programmable

• jkm89
In summary: This should give you a pulse that is accurate to within .5s.In summary, the person is trying to figure out a way to have two signals go above a certain voltage threshold for a period of 0.5 seconds. They are stumped on how to do it.
jkm89
Greetings,

I have two signals, I need a way of testing whether they go above certain threshold voltages for a period of 0.5 seconds. This must be non programmable. I am a bit stumped o how to do it.

I thought of having these signals go into an AND gate and then have that AND gate feed into a timing circuit somehow, but I don't really know how I would design such a timing circuit.

The 555 timer will not work because I need to start the timer, then have it wait, then send a logical high if and when the two signals have been above their threshold voltages.

I have not given much thought yet, but the entry could be a pair of op-amps, to detect the above or under threshold, a 555 as a monostable: the above thresh triggers the impulse, the below thresh resets it. A second 555 is started at the same time and after 0.5s, both results are AND'd. If the first one was stopped, the result would be "0".

I will look into this later today if someone else hasn't given a schematic.

jkm89
welcome to PF :)

it mite really help if you told us all what sort of signals they are ??
give us all the information on what you are trying to do
its pretty impossible for people to give you a good answer without the background

are they audio ? RF ? maybe digital signals

Dave

davenn said:
are they audio ? RF ? maybe digital signals

maybe DTMF.

Would have thought the 555 ideal. Feed an input trigger into the timer to start it off. If output is high and input drops reset timer. If timer times out the falling edge of the output clocks the high input signal into an edge-triggered flip-flop ('74). The flip-flop output will go high only if the timer times out. You can turn this f/f output level into a pulse using another 555 that resets the f/f. For a very fast pulse you might even be able to have the f/f reset itself. Might be a starting point.

Might try a 4 bit counter with a 32 Hz oscillator. By running your anded signal into the clear pin of a 74HC193, you could hold its count at 0 until your condition was met. Then, the counter would wait 16 counts before dropping the carry output. This would be .5 to .53 seconds later.
Another method would be to use an NE555 as a simple level detector. Tie the trigger and threshold lines together with a timing capacitor and a pull up resistor to Vcc. NAND your two signals and use the result to drive an NPN transistor to discharge the capacitor. When your condition is met, the NPN transistor will turn off and allow the capacitor to charge. Upon reaching 2/3's of the supply voltage, the output of the 555 will go high.

Look into Schmitt trigger pulse generator circuits. Theres plenty of examples to generate your pulse. Have one gate to detect the leading edge. One gate to detect falling edge. Latch those two momentary signal and compare later.

I' m on my phone atm but can assist in the rising edge/ falling edge method. There are other ways as well. Depends on your needs.

Edit. I re read the above forgot to say delay the lead edge gate output to an RC Delay of 500 ms and use that to time the slowed down lead edge with the falling edge with another AND gate

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## What is the purpose of testing signals above threshold voltage in non-programmable devices?

The purpose of testing signals above threshold voltage in non-programmable devices is to ensure that the device can properly function under normal operating conditions. This testing helps to identify any potential issues or weaknesses in the device's design, and allows for adjustments to be made before the device is mass-produced.

## How is the threshold voltage determined in non-programmable devices?

The threshold voltage in non-programmable devices is determined through careful analysis and testing of the device's design and components. Depending on the type of device, the threshold voltage may vary and must be specifically tailored to ensure optimal performance.

## What is the significance of testing signals above threshold voltage in non-programmable devices?

Testing signals above threshold voltage in non-programmable devices is significant because it helps to ensure that the device is able to handle high levels of voltage without malfunctioning. This is particularly important in devices that are used in critical or high-risk applications, such as medical equipment or aerospace technology.

## What are some common methods used to test signals above threshold voltage in non-programmable devices?

There are several methods that can be used to test signals above threshold voltage in non-programmable devices. These include using specialized testing equipment such as oscilloscopes or multimeters, as well as conducting simulation tests to mimic real-world conditions.

## What safety precautions should be taken when testing signals above threshold voltage in non-programmable devices?

When testing signals above threshold voltage in non-programmable devices, it is important to take proper safety precautions. This may include using protective gear, following specific testing procedures, and ensuring that all equipment is properly calibrated and grounded. It is also important to have a thorough understanding of the device's design and potential risks to avoid any accidents or damage.

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