ultra sonic xmitter and rec.

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mikeb
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ultra sonic xmitter and rec.

Post by mikeb » Mon Mar 29, 2004 8:22 pm

hi guys i tested the transmitter at the output to the transducer with a frequency counter and i measured a squarewave at 39.996 khz i think this might be acurate enough that the reciever should not suffer so much as far a recieving the signal.
i also measured the signal at the reciever when its detected while the xmitter is transmitting at 39.996khz . the rec. signal all depends on how close the object is to the recieving transducer. at less then an inch the signal is at approx. 10 to 14 khz but never close to 39.996khz the farther away the object the lower is the measured frequency. up to about 2 inches away, then the frequency falls off which is about 400hz

mikeb
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Re: ultra sonic xmitter and rec.

Post by mikeb » Mon Mar 29, 2004 8:28 pm

ed no i didnt buy the whole kit i did just buy the transducers and crystal, and the crystal is quartz can (digi-key) type, looks more like a surface mount crystal but it is resonating at 40 khz

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Edd
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Re: ultra sonic xmitter and rec.

Post by Edd » Wed Mar 31, 2004 11:12 pm

You hopped the thread.
Looks like all of your units are having an intercommunication conflict, all the way from a spectrum spread of 40khz-433mhz..hi….hi.
Well, with your info in the 40 KHz output from the xmitter the suspicioned fear of an inactive xtal is allayed.
Seems like a fault in your receiver is now more in order, due to it being more complex and more room for error. Also if a self made PCB was etched there is the potential of an overlooked foil bridge or an open etch away of a foil path. On the receive first two stages, a scope would be most useful, but a metering of pin 8 should reveal one hefty level shift unless there is a loss /malfunction in the earlier stages. For sure you’ve already evaluated different settings of R23…probably, real quick.
If you were worrying about the receive bandwidth of the receive element I’ve seen them utilized in commercial applications with a variance of 37-42 khz on their incoming signals while receiving an inline signal from about a max of 20 feet distance.
Also on your transducer units, am I correct to assume that one of the pins coming out of the back shell is connected to the whole metal shield. The internal piezo elements are bipolar, but in connecting up circuit wise, there would be a slight advantage to have the shielded pin go to 2x11x9x14 junction on the T unit.
On the R unit having the floating pin going to #3 of the 324 would be optimal.
Any chance your 324 is socketed wherein you could sub in another 324. Lacking that, you could make some degree of analysis by taking a 4.7k res from +5 VDC and use its open end and make contact to enact an ~1/2 second duration voltage on shift at about a 2 second off time period.(Or, if you have done logic work you might already have a logic pulser as were incorporated into some logic probes ?) Start initially at pin 2 then move on to 3 of 324 while DC meter monitoring of pin 1. for a corresponding voltage shift response. Even a cheap analog meter (or a digital one with auxiliary LCD hash marks on its scale) would be helpful here….as compared to a slow scaling digital readout. Then move on thru 5 and 6 monitoring 7 and lastly to 9 and 10 while monitoring on 8.<p>BTW on your RF units what brand and model were they, as some mid range to top of the line units incorporate SWIF frequency determining elements in their design…rock solid, no tuning even involved.
From what you describe on your results of hand capacitance , if both units have a good ground plane, you might not.<p>73's de Edd
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