PING)))™ Ultrasonic Sensor

[Electronics4you]

Hi All,

I need some help with a strange electronic components. In the PING)))™ Ultrasonic Sensor datasheet I found an Echo Hold-off value (time from fall of the trigger pulse to the echo is received) of 750µs, but on their website and several others the value is 350µs. What's the right one?

The delay before next measurement is stated to 200 µs, but this time is for the SRF05 50ms. A grand different but can it be true?

Help with some theory:
I trig the sensor with a >2µs impulse. What happens next? Does it wait for 750µs(or 350µs) until it can receive the first pulse if target is only 2cm away?
It sends out 40kHz impulses for 200µs and then it receive an echo at sometime, and sometimes in the mittle of the transmitting.

Datasheet PING))): https://www.electro-tech-online.com/custompdfs/2006/05/28015-PING-v12.pdf
Datasheet SRF05: https://www.robot-electronics.co.uk/htm/srf05tech.htm

 

[StopGo]

Just looked at the PING datasheet (your 1st link), it seems to be using the same pin as both input for the trigger and output for the echo signal. The holdoff might be to allow the microprocessor time to reprogram the port pin as input.. otherwise an echo might cause the SIG pin to start driving TTL levels while the micro was still set as an output.

I'm thinking you have to subtract the holdoff time from the actual measured time between trigger and echo pulse, and to reconfigure the port pin as input before the holdoff time expires.

 

[akg]

the hold off value is there , because after the transmission there will a 'ringing' in the transducer, so if u switch to receive mode immedialty u get a false reading, it takes some time for the ringing to die out .

 

[rockin_rick]

Hi All,

I need some help with a strange electronic components. In the PING)))™ Ultrasonic Sensor datasheet I found an Echo Hold-off value (time from fall of the trigger pulse to the echo is received) of 750µs, but on their website and several others the value is 350µs. What's the right one?

Check the Parallax forum, there was a question and official answer to this posted (about a month ago, IIRC). The hold off time changed along the way. (I don't remember which spec is correct.)

Rick