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Them Chinese are clever

A while back I got some ultrasonic distance sensors from ebay:

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The main idea was to try to use this as wind speed meter, but also curiosity how they did that at 5V DC, as I needed in other experiments many tens of volts for a reasonable signal.. Well, them Chinese are clever, they use the MAX232! Here is a circuit diagram:

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By driving the piezo in a bridge from the RS232 output of the MAX232, they could get 24 Vpp (+12 to -12 V). The MAX232 does the voltage generation.

It is an old trick, I have used MAX232 to make a negative supply for some opamps once... But you never are to old to learn a trick, could be used for other things too, like alarm beepers.

This one shows the RX filter:

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This sensor works very well actually, I removed the TX piezo side and put it 30 cm away with some wires, and was testing pulse length variations while making wind with a big fan, very hard to see, unknown micro ?

But for the sensors worth the money.

Replace micro and software, there is the ultrasonic wind speed meter.

Maybe it is already on ebay ;-)

Reply to
Jan Panteltje
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interesting use of a charge pump chip..

I believe I showed a circuit that I employed in a very simple design where I needed a -V on the Vee side of a Lm324 chip ?

I used a spare op-amp to generate a pulse which in turn drove a tranny for a very simple buck boost, which provided the (- Vee) volts for the same LM324 chip.

In the end, the whole circuit operated fine with a 9 volt battery with a +/- dual supply, self generated - rail from that one chip.

Jamie

Reply to
M Philbrook

If you know which pins to tap you don't need to run it through the drivers. (this can be determined by inspecting the data sheet)

use a bigger capacitor.

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umop apisdn
Reply to
Jasen Betts

On a sunny day (6 Jun 2015 12:58:35 GMT) it happened Jasen Betts wrote in :

Yes I took it directly from the '-' cap.

Reply to
Jan Panteltje

On a sunny day (Tue, 02 Jun 2015 05:28:54 +1000) it happened Clifford Heath wrote in :

Yea, Joseph Swan invented the lightbulb:

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Reply to
Jan Panteltje

On a sunny day (Tue, 02 Jun 2015 05:28:54 +1000) it happened Clifford Heath wrote in :

Yea, but this is now about wind-speed, see me demonstrating the effect of air speed on phase, it is easily measured:

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Here I do the same phase compare with 'reflections':

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Those were just old remote control piezos, I did that experiment a few years ago, back then I was driving the piezo with a LC oscillor, that is why I was curious how those very clever Chinese were driving it.

As you can see plenty of signal.

Reply to
Jan Panteltje

It's TVG (time-variable-gain), commonly used in sonar and ultrasound. I designed my first TVG for ADR Ultrasound ~1975. IIRC gain was variable linearly in dB's. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

On a sunny day (Sat, 06 Jun 2015 07:19:23 -0700) it happened Jim Thompson wrote in :

I was counting 3 seconds / km from lightning flash to thunder sound long before that. ;-)

Reply to
Jan Panteltje

I think 1 second / 1000' is more accurate ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Not when you are timing by counting, "one one-thousand, two one-thousand, three one-thousand".

--

Rick
Reply to
rickman

on a really cold day you'd be right, by my arithmetic 333m/s is the more accurate at temperatures above -40

--
umop apisdn
Reply to
Jasen Betts

For the ultrasound application it _was_ TVG. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

On a sunny day (Tue, 02 Jun 2015 22:46:24 +1000) it happened Clifford Heath wrote in :

My demo on youtube uses Doppler only. That means there is no 'ping', as the transmitted signal is continuous. In the first video I use the Lissajous figure on the scope with x for transmitted and y for received, to see the phase shift:

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In the second what you see is the sum for the signal received directly from the transmitter versus the reflected signal from the eraser gum (and my fingers).

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You see the minimum ever so many mm (= period).

Reply to
Jan Panteltje

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