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LAB PROJECT(similar to Hugo Game)

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elvinme

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Dear friends.
For lab project we are required to design a circuit diagram which can transmits different frequencies and a reciever] which recieves corresponding frequencies. The lab project is very similar to hugo game. Like hugo which can be controlled by telephone frequencies we are asked to design a reciever parts which can read the transmitted signal . And each frequency corresponds to LED connected to lit. The Project consists of two parts Reciever part and Transmitter part. i have 3 days to submit this pre-report please help. What are the basics of this design. The diagram is as follows:


View attachment 64145


we are allowed to use any of these equipments:

any types of resistors, capacitors, inductors, diodes, LEDs, op-amps and
transistors

THANKS
 
please just give some idea how to build this circuitry
I mean how to generate frequency by transmitter part
 
I seriously doubt you was given 3 days to complete a write up :p, smells a bit country side to me!

Anyway the mention of telephones (I have no idea what Hugo is!), and summing amplifiers makes me think your meant to be building a DTMF system (Dual Tone Multi Frequency).

If this assumption is correct, you will probably not have to implement all tones, as this would be quite time consuming but the basic idea is you have 8 oscillators. Pressing a key sums the output of two oscillators as per the keypad function table here https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling

You will then amplify this summed signal such that you can drive a small speaker.

Receiver wise you will need a preamp, and some way of detecting if certain tones are present. With such limitations I would probably go for 8 high Q filters, with the output of each being envelope detected.

You could then use opamps as comparators (with hysteresis) on these envelope detectors and make AND gates to determine which button was pressed (i.e. each button will contain two tones).
 
Call the tutors bluff and use an MV8870 device. It contains all the above components, just you didn't design them. :)
Decoding DTMF tones reliably requires high Q filters (possibly switched capacitor filters or digital filters).
Trying to do this with op-amps will require very high stability components in several filters of many orders.

If I have missed something and DTMF is not the issue then choose two frequencies as far away from each other as possible and use a PLL (from discrete components will be a laugh in three days) to detect the signal.

From experience, don't be afraid to challenge such requirements. Most tutors are pure academics and have never worked in an industrial environment. My control theory lecturer often gave us aeroplane control systems to analyse that were inherantly unstable. He had spent a year in the aerospace industry then moved into teaching....and it showed.
 
Could throw your instructors a real curve ball and decode with goertzel algorithms on a micro-controller :). Trouble is some instructors can be strict about such things...
 
hi RitchTheDude. I have already found some idea about how to design. I assume you have looked my uploaded block diagram.
the thıngs are not that much complicated. We think that we can design a sinusoid generator with the help of Op-amps and we can control frequency of output signal. We will design two of them sınce we should have 2 frequencies hıgh and low. We have a problem at this point .how can we add those sıgnals frequencies? for examle we will generate 2K Hz and 400 Hz and we would like to add them up such that we get 2.400k signal frequency .and also we will design reciver part with band pass fılters allowing to pass certain frequencies with LED indicarors.
 
hi RitchTheDude. I have already found some idea about how to design. I assume you have looked my uploaded block diagram.
the thıngs are not that much complicated. We think that we can design a sinusoid generator with the help of Op-amps and we can control frequency of output signal. We will design two of them sınce we should have 2 frequencies hıgh and low. We have a problem at this point .how can we add those sıgnals frequencies? for examle we will generate 2K Hz and 400 Hz and we would like to add them up such that we get 2.400k signal frequency .and also we will design reciver part with band pass fılters allowing to pass certain frequencies with LED indicarors.

You don't want to add the two frequencies to make a third frequency. What you want to do is to add the two voltage waveforms to create a signal where each tone is still present, so that they can be separated out by the bandpass filters at the receiving end.

What you want is a "summing amplifier" which is a fairly common op-amp configuration.
 
You don't want to add the two frequencies to make a third frequency. What you want to do is to add the two voltage waveforms to create a signal where each tone is still present, so that they can be separated out by the bandpass filters at the receiving end.

What you want is a "summing amplifier" which is a fairly common op-amp configuration.

thanks friend


But for the receiver part should we use two filters for determining signal with two frequencies?
if we use two filters then what will be the configuration ? will they be in series combination?
By the way we are required only 4 button
 
To encode 4 buttons, you will need four frequencies. Either one freq per button, or the dual frequencies like DTMF. One big advantage of dual frequencies is that the probability of two frequencies showing up at the same time in random speech and music is far less than a single frequency occurring. (which happens all the time)

Each switch will have a 'row' frequency, and a 'column' frequency. So, for a 2x2 switch array, you will need to two row and two column frequencies.

Pressing a button on the original Bell system DTMF keypad closed two switches. One would select a tap on an inductor to generate one of the four the row tones. The other switch would select a tap on a 2nd inductor to generate one of the column tones. There was probably a third switch to apply power to the oscillator.

You need to do something similar. Either with four different oscillators, or two oscillators and a means to make each oscillator run at two different frequencies.

At the receiving end, you need four bandpass, or notch, filters. One for each frequency. The inputs of each filter are in parallel. You may need an input buffer amplifier to control the source impedance that each filter sees.

Then use a some logic circuitry to decode the pairs of of tones into the four discreet on/off outputs.
 
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