I want to make something similar to a ping scan robot, but my budget is low.
As Ultrasonic ping sensors are a bit expensive and cheap HC-SR04 are not available in my country I am searching for alternatives and I found 40kHz ultrasonic transmitter and receiver pair over here Probots - Largest DIY Electronics, Robotics & Engineering Parts Buy Online Store Buy Online India .
But I've no idea of their quality and range. I tried searching for data-sheets but I had no luck finding a good on.
Can someone tell what their range and accuracy is when compared to ultrasonic ping sensors. Also is an external circuit requires or can they be connected or can they be connected like an ir led and phototransistor.
Ufoguy:
I want to make something similar to a ping scan robot, but my budget is low.
As Ultrasonic ping sensors are a bit expensive and cheap HC-SR04 are not available in my country I am searching for alternatives and I found 40kHz ultrasonic transmitter and receiver pair over here Probots - Largest DIY Electronics, Robotics & Engineering Parts Buy Online Store Buy Online India .
But I've no idea of their quality and range. I tried searching for data-sheets but I had no luck finding a good on.
Can someone tell what their range and accuracy is when compared to ultrasonic ping sensors. Also is an external circuit requires or can they be connected or can they be connected like an ir led and phototransistor.
I show 3 ICs and at least 20 other components on the back of ultrasonic sensors that use those transmitter and receiver pairs as you reference. So, it would seem quite a task to turn the transmitter and receiver pair into a SR04, and my guess would be it would cost far more than the SR04.
I've got to imagine you could find a SR04 in India, it's probably where they're all made. But, even if not available in India, why not just order it from outside India? Seems there's lots of places in Hong Kong with the SR04.
Tim
The usual method to drive the transmitter is with a step-up transformer as something more like 50V is needed to get decent power out of a piezo transmitter. You want a sensitive amplifier on the receiver to boost its signal level, and a 40kHz bandpass filter to tune out noise.
I've seen circuits where the transformer is part of a tuned circuit so it can act as receiver filter as well as transmitter booster, sharing a single transducer - the receive amplifier has to be protected from the transmit voltages though, so its a little more complex.
There are a number of very cheap car-reversing sensor kits available that contain 4 ultrasonic transducers and all the electronics to drive them - reverse-engineering and adapting them to a different use might be quite tricky, but would then probably the cheapest way to get 4 ultrasonic proximity sensors
MarkT:
but would then probably the cheapest way to get 4 ultrasonic proximity sensors
Cheapest way would be to purchase four $5.00 USD polaroid spectra or Sun 660 cameras from Goodwill on half-off day (so a total of $10.00 USD); cheapest set of Senscomp 6500 equivalent sensors you can ever find. Although such Polaroid cameras are becoming more difficult to find as the days go buy (I purchase every one I come across that sells for under $10.00 USD).
hahaha do they have half off day at the goodwill in India?
If you look carefully, you can probably find the schematics for something like the SRF04, and you could almost certainly lose the PIC processor and bit-bang the output driver from the Arduino.
You'll still end up with a couple of square inches of discretes and ICs, which you'll have to debug yourself.
So, when you factor in time and the cost of an oscilloscope, the ready-made devices look pretty good value.
OK. I get it. I've to make the ping sensor all by myself. No can do. I thought I could use them directly by connecting to an analog input and a power supply. 
I've seen designs that figure out a logic input's threshold voltage, then jack up a source to just below logic one, then allow the millivolts provided by the echo return to tip it over the threshold.
I still suspect it's a job for a scope
This is how I do it
single channel
2 channel
Both versions of the receivers have 2 stages of x100 gain.
The amps are TL084 J-FET input op amps, because these are "dual supply" and I'm running them on a single 5V rail, I set the centre voltage with a voltage divider.
The second amp has a gain control, it's output is AC coupled to a Schmidt trigger 7414 inverter.
The trimpot sets the threshold.
Version 1A is a 2 channel RX, Version 1B a single.
Version 2 has filters for 30khz and not only is a waste of time but a head %@$@ to setup, let alone debug!
It's simply not necessary for the sort of range we are talking about.
The transmitter is a simple push/pull circuit made from a 7400 quad NAND gate.
Again keeping it simple works really well.
As for the talk of hitting the Tx transducer with 50V is kinda silly, we are talking about ranges of less than 10 metres, not building a dog "trainer" or depth sounder!
As I've shown here, you dog or cat will still NOT like it that much close up!
My clock circuit looks like this
I did it this way because I had a 30Mhz clock module lying around, probably on a video card.
30Mhz / 3 = 10Mhz, that gets divided by 10 to get 1Mhz, which I use to derive a 100Khz and 10Khz for the distance counters.
Counting @100khz gives a minimum resolution of 3mm, counting @ 10khz a minimum resolution of 3cm.
To derive the 40khz Tx source I divide the 1Mhz clock mentioned above by 2 stages of 5.
This circuit is the single channel 8 bit range counter
The 3 channel version
Counting @10khz, 1 count is1x10^-3s or 3.41cm, an 8 bit count, 256, gives a max range of 8.7m
Counting @ 100khz, 1 count is1x10^-4s or 0.00341m, an 8 bit count, 256, gives a max range of 87cm
I built this to use with my SYM-1, a 6502 running @1Mhz, which is why I'm using 3 counters.
There was enough "lag" when I tried using a single counter with 3 receivers, pinging and polling each one, that if the object you were ranging was moving the output was unusable.
By pinging the Tx, then counting the interval from each Rx we were able to get the SYM to "drive" a small car around a track.
I'm using the Tx and Rx circuits "as is" on my Rover 5, 3 for ranging in front, giving 90 degree coverage.
In addition I'll put another pair of Tx/Rx pairs on each side.
Because the Arduino is 16+ times faster than a 1Mhz, 6502, I'm going to use the digital output from the 7414 Schmidt trigger to get "gross" range and use 3 analogue pins to measure analogue amplitude direct from the receiver.
While you don't really need a CRO to set this up, if you watch the output you can see an amazing amount of detail on the CRO screen.
With a single Tx/Rx pair being triggered at regular intervals then holding your hand in front of the "beam", you can actually see the shape of your hand and fingers!
I'll shoot some video of my DSO Quad and post it on YouTube.
If you haven't messed around with analogue sonar, I recommend you try it, just for the "Wow" factor! 
I already have SR04, but i need to measure the frequency transmitted from another oscillator. Anyone help me out plz... 