Ultrasonic Range Meter

Schematic

LED => Transducer...the non visible end of transducer is grounded via a resistor...

roots_of....

Why 12V supply ? In my opinion 5V is enough, take a look here

Stef Mientki

Schematic

LED =>

Transducer...the non visible end of transducer is grounded via a resistor...

roots_of....

Im looking for a range of about 10cm- 6m, and i didnt think that a 5V supply would be enough to drive the transducer hard enough to get the range i desire. And specifically 12 v supply, because i am using a 12 v car battery.

And i was also thinking that i will need a voltage regulator after the

12V battery, which will then leave me with a voltage of around 10.5 V.

i would like to use a driver circuit because the transducer is highly capacitive and i didnt think i would be able to get sharp rise and falls in the pulses i wish to transmit otherwise. In the schematic below i have used schimdt trigger chip. But i want to use a driver chip, something apart from the schimdt trigger.

Hi, Roots O' Culture. Your transducer can be seen as a capacitive load. You're basically trying to do this (view in fixed font or M$ Notepad):

| | .---------------. | | | | | | 5V-to-12V | | | Level Translation/ | | | High-Current source/sink | | | Buffer | | | (Non-Inverting) |.--.| (Inverting) | | | |\\ || || /| | | PIC o----o-----| >-----|| ||-----O< |---. | | | | |/ || || \\| | | | | | |'--'| | | | | | Transducer | | | | | (1800pF) | | | | '-------------------------------' | | | | | | | | | | '---------------' | (created by AACircuit v1.28.6 beta 04/19/05

Since you're already going with a PIC, Microchip has a pair of drivers that will do exactly what you want -- the TC4420 (non-inverting) and the TC4429 (inverting) high speed MOSFET drivers. They have the capability to drive up to 6 amps with low Rds(on) MOSFETs built in, and the IC takes care of the level translation for you. Put one on each side of the transducer, and you're good to go. They're made to drive capacitive loads, and have crossover protection built in. They'll smack that T/R40-16B around real good (140 volts max!?! Is that an aluminum, steel, or titanium case?).

Unless this is a high volume application, I don't think you're going to be able to do better than this. The ICs are available in 8-pin DIPs, too (CPA suffix).

Here's the datasheet:

If you want to be really safe, add a 2.2 ohm non-inductive resistor (a

1 watt carbon comp is good here) in series with the transducer to limit maximum current doesn't exceed 6A.

| | .---------------. | | | | | | 5V-to-12V | | | Level Translation/ | | | High-Current | | | Buffer | | | (Non-Inverting) |.--.| (Inverting) | | | |\\ || || ___ /| | | PIC o----o-----| >-----|| ||--|___|----O< |---. | | | | |/ || || 2.2 ohm \\| | | | | | |'--'| | | | | | Transducer | | | | | (1800pF) | | | | '-------------------------------------' | | | | | | | | | | '---------------' | (created by AACircuit v1.28.6 beta 04/19/05

On the power supply end, the TC4420 and -29 are good to 18V, so you shouldn't need another regulator. You also want to maximize voltage. I'd recommend using another 2.2 ohm series resistor or choke and a large (2200uF or greater, 25WV) cap with a Transzorb for a localized charge source and to protect against load dump.

| |Battery ___ To XDCR Power |B+o----|___|--o---o->

| 2.2 ohm | | | +| /-/ | 2200uF --- ^ P6KE16A | 25WV --- | | | | | | | | === === | GND GND (created by AACircuit v1.28.6 beta 04/19/05

Good luck Chris

Try these links.

Andrew.

Chris, Thanks, that has solved my transmitting circuit.

Andrew, you are right TC4420 is not available at hand locally, but Farnell ( $4.40) delivers within 3 days, so that is good. Though in order to get going im using the TC4428CPA, it has a low Rds(on) 40 ns.

As for the recieving circuit, i saw a design from national in the Electronic Design (jan 2006) journal. it uses a 2 stage LMP7711 (17MHz) as active filters (band pass), with a gain of 100 * 10, but these are not available locally either. I am trying to find substitutes.

Chris,

right TC4420 is not available at hand locally, but Farnell (

within 3 days, so that is good.

TC4428CPA, it has a low

saw a design from national in the

uses a 2 stage LMP7711 (17MHz)

100 * 10, but these are

substitutes.

My receiver is a POS affair without automatic gain so I've set the transmitter PIC to be able to PWM at two different rates and as yet the bandpass filter eludes me (rank novice). Need to do more research when I'm fresh. I'm using the Dual LM833N 8pin DIP (Min 10MHz, Max

15MHz), high slew rate. I'll have a look at the LMP7711 too.

Regards,

Andrew.

HI, Andrew. The sun never sets on Farnell (I'm in the States -- it's Newark here). Unfortunately, the Farnell website is being updated. But looking at the Newark site, it seems they have the same issue.

You may want to try the TC4426 (dual inverting) and TC4427 (dual non-inverting). You'll have to leave half of each chip dormant, unless you have something else to do with them. To my recollection, you can't parallel outputs safely.

The datasheets for the TC4426CPA (8-pin DIP, commercial temp range) and TC4427CPA are available at the Microchip website:

The datasheet says they're rated for capacitive loads, and after all, this isn't continuous use. You're only snapping the transducer a couple dozen times, eight to twelve times a second. You really shouldn't need a series resistor with the transducer unless you're really cautious, especially considering the Rds(on) is typically 7 to 8 ohms. But by rounding the edges of the transition with the additional Rds(on), you're losing some power.

Good luck Chris

Chris,

Great diagrams and advice. I've been trying myself to create a simple but "as long a range as I can get" ultrasonic remote control using the same transducers and 16F628A PICs. The transmitter uses an AND gate to switch a 100V N-mosfet with the transducer, 1000uH inductor and a

100ohm resistor. At 9.5V, 60% duty cycle sending two bytes over and over at 300bps it does work up to approx 11 meters from the receiver. I'm working again on a bandpass filter for the receiver and once I figure that out I'll need help hopefully from the members of this group to get an automatic gain cirucuit built. The last time I fiddled with bandpass filters I cut the range down to two centimeters! Not much of a remote then!

The initial link that roots_of_culture provided for the transducer PDF is a Jaycar branch in New Zealand and assuming that he too lives here then acquiring the drivers may be a problem for both of us.

For roots_of_culture - one company, South Island Components, is trade/retail has only the TC4429CPA but doesn't stock the 4420 while other retail outlets like Jaycar, Dick Smith and Altronics don't stock them or any of the range at all. RS components deals with the trade and requires a company account to be opened but they do have the: TC4421CPA - 9A Single Inverting TC4426CPA - 1.5A Dual Inverting TC4427CPA - 1.5A Dual Non-inverting TC4428CPA - 1.5A Combined Single Inverting and Non-invereting TC4429CPA - 6A Single Inverting (Note - RS sells the TC4429CPA for NZ$10.70 + GST eachwhile South Island Components sells them for NZ$5.48 + GST) Other than trying a few more companies I've found online in the Yellow pages there's Farnell in Australia I suppose. Should my assumption be correct and you do find a source for the TC4420 in NZ could you please post it in this NG as I'd greatly appreciate that.

Regards

Andrew.

My receiver is a POS affair without automatic gain so I've set the transmitter PIC to be able to PWM at two different rates and as yet the bandpass filter eludes me (rank novice). Need to do more research when I'm fresh. I'm using the Dual LM833N 8pin DIP (Min 10MHz, Max

15MHz), high slew rate. I'll have a look at the LMP7711 too.

Regards,

Andrew.

First off it was rude of me not to thank you in my last post for the Farnell source confirmation - Thanks.

Secondly where did you get that Electronic Design Jan 2006 publication from? I've looked on the net, found its publisher (Penton Publications) and searched the CHCH city libraries to no avail. The Electronic Design website is only a front page that constantly reloads itself. The Europe one wasn't helpfull either.

Regards,

Andrew.

Sori for late reply.. was away... Found the journal in the Manukau Library- looked in national website, below is the link

hope it helps

I only today noticed that Radio Shack is selling a completed ultrasonic ranger as part of the VEX robotics stuff they sell. Everything is "half off" until June, I'm told. The ranger is normally $29.99 but is now selling for $14.99. It uses 5V supply and 3cm to

300cm ranging with 40kHz. Paperwork says it uses a 10us pulse; but with a 25us single cycle width I doubt this spec. I might believe 100us, though, or 4 cycles. (Their minimum distance of 3cm corresponds to a trip time of 175us.) Comes with screws for mounting and a nice enough enclosure.

Just to let you know...

Jon

Thanks,

Andrew.

Hey Chris, I'm doing a project on ultrasonic ranging too and the desired distance is 50m. It seems rather far and I wonder if TC4420/4429 could help? And can you explain how these things work cos I'm really confused about how

6A would help driving my transducer. :-/ Thanks Martin

Hey Chris, I'm doing a project on ultrasonic ranging too and the desired distance is 50m. It seems rather far and I wonder if TC4420/4429 could help? And can you explain how these things work cos I'm really confused about how

6A would help driving my transducer. :-/ Thanks Martin

Hi, Martin. I'm no expert on this stuff, but am generally interested. But it seems to me that 50m really is a far distance. Two problems pop into mind -- (1) energy spreads out (ignoring dissipation of energy at 40kHz in air) at D^2 and returns with another D^2 factor, so this suggests to me a D^4 hurdle to overcome and that would mean a lot of initial energy (read as very high driving voltage) to get there; and (2) reasonable resolution over that kind of range seems vaguely problematic, too. I also don't know what the attenuation of the usual

40kHz is in (wet) air or if there are better or worse bands nearby you might prefer. I wonder if there is a page documenting it over frequency...

Have you found any existing ultrasonic ranger that works at 50m?

Jon

Hi Jon, I think 50m is way too far too actually. There's this paper on ultrasonic ceramic transducers on

and it explains all the losses and such. For a 100V pp driver with a transducer's SPL of 108dB and the receiver's sensitivity of -75db, according to my calculations, the voltage at the receiver at 50m is about 0.2uV :)) With the help of a cone I think this could get up a bit but still... Do you think I can do anything with this?