ultrasonictransducer.wps-3.doc

8/14/2019 ultrasonictransducer.wps-3.doc

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The Ultrasonic Transducer Transmitter and Receiver

To My Valued Customers:Id like to take a second before I start to say thank you to all that chose to shop at the HobbyTronixStore.

It is a small business that I run on the side, and its good to know that in these poor economic times, there

are still people out there who share the same interest and passion towards electronics that I have. Thanks to

all of you. I hope you find this document useful.

Sincerely,

Patrick Mitchell

Electronics Engineering Technician

HoyTroni!Store "###$electroniclessons$com

%ET&S 'ET ST(RTE)*

kay! So in every electronic circuit, there must be a power supply, correct" #ell in this care were going

to need three different supplies. $ont worry, youre not going to really need three different sources of

power. nly two. %irst of all, were going to construct our power supply for the ultrasonic transmittercircuit. &s you can see below, all we need is a 'v battery(connector )%ully charged battery*, and two

capacitors. +ow, if youre using a battery, you dont necessarily need the two capacitors. Its ust goodpractice to implement them. If youre using another source of power- perhaps an & to $ wall

transformer, which I dont suggest you do, then the capacitors are a very good idea. I greatly advise that

you use batteries for this proect.. That being said, the power supply circuit is really up to you. /ou can

customi0e it, and go all out with protection and what not. However, if youre taking my advice, and using a

'v battery, I wouldnt worry too much about noise effecting the performance. #e have to worry more

about noise at the receiver than we do at the transmitter, so dont waste too much time worrying about it. I

dont suggest using a power supply larger than '1$. If you decide to use a wall transformer, I suggest

actually testing the output value with a multi2meter before using it. Ive found several wall transformersthat are rated to output '1$, and actually output 342351$, so beware.

THE TR(+SMTTER CRCUTThe really neat thing about these transducers is the fact that they are designed to transmit and receive. If

you have two ultrasonic transducers, you can send and receive. f course youll need two breadboards or

two 67s. 8ets talk about the transmitter, shall we" I have personally tested these transducers are

fre9uencies as low as 4:kH0, to as high as 5:kH0. /ou can still transmit and receive information at these

fre9uencies, despite the fact that the center fre9uency is ;:kH0.

n the following page, youll see a diagram for the transmitter circuit. Ive offered a part list, but there are

many passive component values )resistors(capacitors(transistors* that can be modified to achieve
http://www.electroniclessons.com/http://www.electroniclessons.com/http://www.electroniclessons.com/


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maximum output power. The part list I am offering is a


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I sure hope you have an oscilloscope. If you dont then I hope you have been careful in making your

connections. 6lease refer to the transmitter diagram on the previous page.

3* #ith your oscilloscope, probe the following areas while pressing down the transmit button.

2 6inBD of the 555 timer.2 The first pin of the transducer- the pin connected to the middle of the voltage divider.

2 The second pin of the transducer that is connected to ?D, and the collector of the +6+ transistor.

/ou should see a waveform on your oscilloscope screen at each of these test points. THE/ #I88 +T

&88 8F THE S&GE. /our main point of interest is the pin of the transducer that is connected to ?D

and the +6+ transistor. &re you able to see a decent waveform here" If not, then you may have a problem.

If so, you should be ready to move on to the receiver.

4* If you are not getting anything at either of the pins of the transducer, then check your connections. If

you are not detecting any waveform coming from your 555 timer, then go back and check your connections

again. /our 555 timer should be working perfectly. Is your 555 timer properly grounded" Is it properly

powered by the 'v 1 line"

D* Is your battery sufficient" 6erhaps youre better off going to your nearest grocery store and purchasing a

'v $uracell or energi0er battery.

;* If all else fails, and youre not able to find the problem, start over. ?emove all of your connections, and

start from scratch. $ont feel bad if this is the case. Ive had to do it a hundred time in the past.Sometimes its ust what you may need. Ive personally re2created this circuit using this guide.

TME T- T(%. (/-UT -UR RECEVER CRCUT

& warning to those of you who may have had a little bit of trouble with the transmitter circuit> The receiver

is only as hard as you make it. Take your time and make sure you care making all the right connections.

The receiver circuit is substantially more complicated.

+ow, since were starting a whole different circuit, were going to need another power supply. I earliermentioned that were going to need three power supplies in total. #hat I really meant by this was that

were going to need to step down our 'v )battery* source by using a voltage regulator circuit. #e only want

to work with 5v in this circuit. $ont use 'v or youll destroy the TT8 components. Here is the schematicfor the power supply.

So lets have a chat about this power supply circuit. &s before, the capacitors are not necessary if youre

using a 'v battery, as batteries are primarily stable. #e want to connect the positive lead of our 'v battery


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&lright. #e have what looks to be another amplifier stage, but really it acts as both an amplifier, as well as

a noise eliminator. %or those of you who have a strong background in electronics, you may scoff at that

statement, but hear me out. Since weve amplified the incoming signal so much, weve also significantly

amplified ambient signals that were picked up by the transducer. #e could implement filters, but we can

work around these signals, as these signals are not common noise. &fter the second stage, we get anambient signal that ranges between :24v in amplitude. This is why were going to employ a comparator

circuit. #e can tune out these ambient signals, and concentrate on the transmitted signal using this circuit

H# IT #?FS>

#hen we have a strong signal being amplified by the two2stage active amplifier circuit, the output of the

second stage should be saturating. 7y this, it is meant that we should be getting what looks like a s9uare

wave from the second amplifier when a strong signal is being received. Since were powering our

amplifiers with a power source of 51$, the maximum output will be about :K of 51$. This meansthat the output is saturating. The amplifier may want to output a higher voltage, but it is limited, leaving us

with what looks like a s9uare wave. So we have roughly a :2;.5 volt signal at the positive input of the

comparator )the third 8GDA, which is LD* when we are receiving a strong signal from the transmitter.

The tuning is accomplished by the use of a potentiometer )63*. Since the ambient signals being picked up

are ranging between roughly :24v, we can manually set the negative input )2* of the comparator to ust

about this voltage amplitude. This will keep the output of the comparator at roughly :v until a strong signal

)425v* is amplified by the amplifier stages. I reali0e this may be hard to grasp if youre relatively new toelectronics, but if you have an oscilloscope, you can leave the output of the second stage unloaded, and you

can probe it with an oscilloscope to view the ambient signal. The middle pin of your potentiometer is thewiper. The wiper is the pin that is attached to the negative input )2* of the comparator. #ith the

potentiometer, we can set the voltage at the negative input to any voltage between :v and 1, which in

this case is :251$.

TM+I+>

So lets get tuning. /ou dont necessarily need to do this now, but why not get a head start" 6robe the

output of the comparator once youve set up the entire comparator circuit and connected signal )&* to the

positive input. 6lug in your battery, and watch the output of the comparator with your oscilloscope. #hatyou may want to do is actually tune down the voltage at the negative input using the potentiometer, to see

an amplified ambient signal at the output. %rom there, we can tune the voltage at the negative input up

slowly, until the output is a flat :v. To reiterate, you will see a messy s9uare wave at the output of the

comparator when the voltage at the negative input is below the ambient signal level. #e want to slowly

tune the voltage at the negative input up until it is ust over the ambient signal voltage amplitude. #hen

this is accomplished, we should see a smooth :v at the output of the comparator. +ow, once youve donethat, use your transmitting transducer circuit to send a signal into the receiver transducer. Tune it so that

you can receive a strong signal from as far away as possible without allowing the comparator to be

overcome with the ambient signal. Experiment with it. It may take a little time to understand what Im


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talking about. Experimentation is the key to learning. Feep that in mind, my friends.

THE )E%(:

/oull have to scroll back to the previous page, to refer to the delay circuit. %or the delay, Ive chosen to

use a C;8S34D TT8 chip. This chip is a re2trigger2able monostable multivibrator. This chip is a 3A pin $I6I. It has two internal retrigger2able monostable multivibrators. #e are only going to use one. The idea is

this. #e are working with higher fre9uencies in this proect. #e will soon be working with a circuit thatwill re9uire single pulses to operate properly. This means that we have to turn several thousand pulses )the

kH0 signal coming from the transmitter* into a single pulse. The C;8S34D acts to do ust that. nce a

digital signal triggers the input )6inB3*, the output activates )turns from :25v*, and a delay will begin. The

delay is determined by ? and D. This delay time is roughly 3(5 of a second in its current configuration.

%eel free to experiment with different values. If the delay starts, and another pulse hits the input pin, then

the delay starts over. #hen the transmitter stops pulsing, the signal at the input pin will stop, and when thedelay runs out, the output of the C;8S34D turns off. Hence turning thousands of pulses into a single pulse.

If you cannot yet grasp this concept, play around with this chip. /oull come to understand the chip. ?ead

the data sheet if you wish. Gake absolutely sure that youve properly made each of the re9uired

connections, or else your circuit will not work. The output signal of the C;8S34D )6inB3D* is labeled as

)7*. #e will be using this signal line for our last circuit.

THE 5%P"5%-P T-''%E S;TCH

%inally! This is the last circuit re9uired to finish this proect. Feep in mind that the circuit can be used for

tons of things. /ou ust need to continue it as you see fit. /ou can use the toggled output of this circuit fortons of things. 8et me introduce you to the flip2flop toggle switch.

The final chip were going to employ is the C;8S3:'& dual 6T NF flip flop $I6 I. This means that we

have two flip flops within the I, and they are activated on the positive rising edge of the incoming

waveform. #e have it configured as a toggle switch. Every time the rising edge of a waveform hits the

8F input )6inB;*, the L output will toggle either from off to on, or from on to off. #e want our circuit to

start in a known state. 7y this, I mean that I want my L output to be off when I power on my receiver

circuit. %or this, we re9uire what is called a power on reset circuit

THE P-;ER -+ RESET:

The use of a resistor and a capacitor allows us to create a short delay. &s you can see, pinB3, which is the

asynchronous input (8?, is connected to an ? network. The resistor acts to slow the current that will be

collected by the capacitor. This means that the capacitor will take time to charge from :25v. #hen the

capacitor charges past roughly 4. volts, the flip flop will act as a toggle switch. However, in the time it

takes for the capacitor to charge to roughly 4.v, the (8? input will regard the voltage at the capacitor as


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low logic, which forces the L output low. nly when each of the inputs )(6?EO(8?ONOF* are at 5v, or

high logic, will the C;8S3:'& act as a toggle switch. To reiterate, when the (8? input is low, the L

output will be low. &fter the capacitor is charged, the circuit goes into operational mode. #e need this

circuit because when power is initially applied, our flip flop may not turn on in the right state. It may start

with the L output turned on )high logic*. #e dont want this. &s well, the other chips may be fidgety whenpower is first applied. Gake sure you employ this circuit.

6inB3A is the 1 pin, and pinB is the ground pin. The L output is tied to a current2limiting resistor

)?3:*, which is in series with an 8E$ )$3*, and ground. %rom here, you can do with this signal as you

will. Interface it with a microcontroller, turn on a relay, activate another circuit, etc. The possibilities are

endless.

TEST TI6S>/ou may want to play around with the resistor(capacitor values for the C;8S34D monostable multivibrator

delay. /ou can customi0e your delay. /ou may want to do this to make the toggle switching a little more

comfortable. Its all a matter of testing, and more importantly, understanding. The hardest concept you

may have to con9uer is the monostable multivibrator. /ou can also play around with your 6ower2n2?eset

resistor(capacitor network. /ou dont need to, but you can minimi0e the time needed for the 6? if you

wish. /ou can also feel free to change the transmission fre9uency. Its all about how you want to do it!

P(RTS %ST

GIS>C8:5 2 5v regulator

8G555 2 555 timer

?3 2 44:?

?4 2 44:?

?D 2D':?

?; 2 5kA

?5 2 3k

?A 2 3k?C 2 3:k

? 2 3::k

?' 2 3:k?3: 2 ;C:?

3 2 :.:3u%

4 2 3:u%

D 2 3:u%

; 2 3:u%S3 2 S6ST

$3 2 ?ed 8E$

L3 2 4+4444

T3 2 $6M3A;:&H34

T4 2 $6M3A;:&H34

L3 2 8GDA

L4 2 8GDA

LD 2 8GDAL; 2 C;8S34D

L5 2 C;8S3:'&

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ultrasonictransducer.wps-3.doc