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How to get time delay of 90 - 120ms using Passive Components Only

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adil.me

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Hi,

I was wandering if anyone can tell is it possible to get 90 - 120 ms time delay using only passive components i.e resisters, capacitors, inductors without using any other active component in the circuit. Thanks.
 

adil.me said:
Hi,

I was wandering if anyone can tell is it possible to get 90 - 120 ms time delay using only passive components i.e resisters, capacitors, inductors without using any other active component in the circuit. Thanks.
Click to expand...

Use R-C low pass filter with proper time constant.
 

What type of signal you want to delay ? Is it a single tone (i.e. sinewave) signal or a different waveform ? Does the attenuation the delay circuit introduce to the input signal matter ?
 

I guess a bucket-brigade device is the proper name for what you seek, there may be schematics on the web.
 

It is a low DC pulse signal of amplitude of less then 2V. There should be NO attenuation to the input signal.

albbg said:
What type of signal you want to delay ? Is it a single tone (i.e. sinewave) signal or a different waveform ? Does the attenuation the delay circuit introduce to the input signal matter ?
Click to expand...
 

So exactly what is the input signal and what do you want the output to look like?
What is the load for this signal?
 

You'll have to accept some distortion of the signal. What is the load?

Depending on the acceptable distortion, a 1st order RC filter might suffice. Or a delay line made from a long lumped element transmission line. Or 30km of cable.
 
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I think you could try to implement an all-pass filter (f.i. a bridged T equalizer). It's composed by L and C and ideally apply a constant delay to all frequency while the amplitude of the signal is not affected. Of course in pratical implementation you will have both distorsion due to non costant delay over frequency and frequency dependant attenuation.
However you should specify the width of the pulse as well as the load seen by this circuit (as already pointed out by both crutschow and mtwieg) as well as the generator impedance.
 

Hi,

Or 30km of cable.
Click to expand...
Yes, a cable could be a solution to keed waveform.
But unfortunately you need 30.000km with speed of light, or 20.000km of RG58 cable.

Klaus
 

KlausST said:
But unfortunately you need 30.000km with speed of light, or 20.000km of RG58 cable.
Click to expand...

In good old days, I saw in some Tekscopes delay lines like pipes; they looked strange those days.

Using speed of sound will be both convenient in terms of budget and space.
 

filip.amator said:
Use R-C low pass filter with proper time constant.
Click to expand...

But in practical using just one RC filter is not a good option to get an accurate delayed signal. Is it possible to make a cascaded filter or any other passive network?

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crutschow said:
So exactly what is the input signal and what do you want the output to look like?
What is the load for this signal?
Click to expand...

The input signal is heart beat voltage generated by some deformable material like piezoelectric which is like pulses of 1-2Hz, I need to delay it for 90 to 120ms without loss in the signal using passive elements only.
 

albbg said:
I think you could try to implement an all-pass filter (f.i. a bridged T equalizer). It's composed by L and C and ideally apply a constant delay to all frequency while the amplitude of the signal is not affected. Of course in pratical implementation you will have both distorsion due to non costant delay over frequency and frequency dependant attenuation.
However you should specify the width of the pulse as well as the load seen by this circuit (as already pointed out by both crutschow and mtwieg) as well as the generator impedance.
Click to expand...

The signal is of 1-2Hz pulses generated by heart beat. So far the load is not defined but we expect to have min. as possible so no losses occur. Which passive network is suitable for low freq. to get delay of 90 to 120ms
 

To those who replied, OP means milleseconds, not microseconds. One RC wont achieve 90 millesecond delay.....
 

A LC filter chain is the only available option for a "lossless" delay filter, it has been already addressed as "lumped element transmission line" by mtwieg. Even if the filter itself doesn't involve losses (at least when considering ideal L and C elements) it has to be driven by signal source with matched impedance which in practice requires a driver amplifier. In so far I'm not sure if the "only passive" requirement can be actually achieved.

In case the passive implementation is substantiated by specific application parameters, it would helpful to hear about it.

The specification yet lacks a signal bandwidth. I presume that you want to reproduce a specific waveform of the "1 - 2 Hz" signal, no idea if 10, 30 or 100 Hz filter cut-off frequency are acceptable. The number of filter LC elements will scale respectively.
 

adil.me said:
The input signal is heart beat voltage generated by some deformable material like piezoelectric which is like pulses of 1-2Hz, I need to delay it for 90 to 120ms without loss in the signal using passive elements only.
Click to expand...
I really hope you don't plan on putting this passive delay network directly on the transducer, with no preamplifier. You need a preamplifier with a low, predictable source impedance.
 

Giro said:
To those who replied, OP means milleseconds, not microseconds. One RC wont achieve 90 millesecond delay.....
Click to expand...

Hi Giro,

Do you know other passive filters for making 90 millisecond and above delay?

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FvM said:
A LC filter chain is the only available option for a "lossless" delay filter, it has been already addressed as "lumped element transmission line" by mtwieg. Even if the filter itself doesn't involve losses (at least when considering ideal L and C elements) it has to be driven by signal source with matched impedance which in practice requires a driver amplifier. In so far I'm not sure if the "only passive" requirement can be actually achieved.

In case the passive implementation is substantiated by specific application parameters, it would helpful to hear about it.

The specification yet lacks a signal bandwidth. I presume that you want to reproduce a specific waveform of the "1 - 2 Hz" signal, no idea if 10, 30 or 100 Hz filter cut-off frequency are acceptable. The number of filter LC elements will scale respectively.
Click to expand...

Yes this is the issue. Can you share some LC circuits for making delay of 90 upto 120 milliseconds.
 

Can you share some LC circuits for making delay of 90 upto 120 milliseconds.
Click to expand...
I'm yet waiting for a bandwidth specification.
 

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