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31  Community / Exhibition / Gallery / Re: Simple Digital Clock using I2C 4-digit 7-segment LED and RTC from Adafruit on: August 06, 2012, 10:46:40 pm
neat, I can see the picture from the second link but the first link:

gives me:

Internet Explorer cannot display the webpage

It may just be my setup but maybe you could check the link.
32  Community / Exhibition / Gallery / Re: Ultrasonic Anemometer on: August 02, 2012, 11:46:37 pm
Have you downloaded the projectreport.pdf.

The circuit is shown there and R22 is used as a threshold set.
Adjust this value to give output only when signal is received.

A CRO picture of the ZCD output is labelled "Output from the zero crossing detector with example program CRO".
33  Community / Exhibition / Gallery / Re: Ultrasonic Anemometer on: July 27, 2012, 11:04:24 pm
A previous question asked:
Then you mentioned the other problem about transducers behavior and define Northerror[20] .
Why 20 values? An again the logic , even is there, not sure to follow why.
This relates to your problem of the differences.

From the project report we compensate using software:

We do run into another problem. Ultrasonic transducers are not symmetric for transmission and
reception. The devices are not linear components and even worse the symmetry changes with
You can match them as north-south, east-west pairs. It's properly a good idea to do so.
However we do need to have a constant which is used to match the pairs as closely as possible.
This constant will need to change with time as the temperature changes.
I use:
int Northerror[20]; //The tof error for north-south transmit
We keep a running sample of the differences when the difference should be zero.
34  Community / Exhibition / Gallery / Re: Ultrasonic Anemometer on: June 03, 2012, 11:30:46 pm
OK I can see what you are doing:

TRANSDUCERS ---- arduino uno ---- Arduino IDE display

Does the calibrate resisitor 1k make any difference. The voltage at analog 5 should change.

If it does not you have a analog circuit error.

If it does and the display "external temperature  =  10.0" does not change you have a program error.

Your job is to find and fix the problem.

The cable:

H1.......................................................long pin
H2.......................................................short pin  NORTH transducer

..........wire 1
..........wire 2  twin shielded microphone cable

35  Community / Exhibition / Gallery / Re: Ultrasonic Anemometer on: June 02, 2012, 11:51:32 pm
it gave me unreal and constant values

I can't follow this. What exactly gives you these values? Is it the Arduino IDE ?

Please provide exact details on what you have connected.

two pin one is short and another one is long

The drive signal is a balanced pair one wire for each pin(long or short). You should use shielded cable which
has a third connection - the shield.
Earth the shield at the circuit board end and leave the end at the transducer unconnected.
36  Community / Exhibition / Gallery / Re: Ultrasonic Anemometer on: April 11, 2012, 12:58:17 am
My question to you is how do you know that this is needed?
What we get is the difference  "diffav" now this value will vary as shown by the wind function.
Using this function we can determine what is needed for a given value.

pick the signal from the sending end
I used twin shielded microphone cable to feed the transducers. Earth the shield only at the circuit board.

I hope the opamps work.  It will simplify the circuit layout.

37  Community / Exhibition / Gallery / Re: Ultrasonic Anemometer on: April 05, 2012, 01:01:44 am
On a rocking sail boat it should be as accurate as an eggcup type. I have used the same response time constant.

why the ZCD  has a pot R 22 ?
We want to detect above the noise level and I want it to occur before the envelope detector. An improvement would be for the ZCD to be fixed and the envelope to be adjustable.

D1 , on the envelope detector.
This is not a rectifier but an Amplitude modulation detector. A precision rectifier would bring the detection level down but I dont know if it is really necessary.

On the 4052, why we need -5 V?
This may be a bit of overkill as the negative voltage on the analog input is very small(it can cope with -5v).
You should try to leave it out and see if it works for you.

What I mean if we send pulse 1 , the corresponding reversed pulsed will be after 300 other pulses
Yes but remember we are getting an average over time.
Also I found that you need a couple of pulses before the circuit becomes stable(I drop the first couple of measurements).

It looks like if the diff is less than 200 (ie half period), then you add a pulse.
I need some more information to answer that.

about transducers behavior and define Northerror[20] .
Now this was just trial and error and I chose 20 as a reasonable figure. This is an area were there could be much improvement.

Even you mentioned that we do not have individual Tof, I think we do have it, since envelope measures that
Yes we do not have an accurate figure for tof to use in that equation.

Keep me informed on your progress.
I am going to revisit this design  as my next project but I will be busy on another project for some months.

38  Using Arduino / Sensors / Re: Ultrasonic Anemometer on: March 15, 2012, 11:57:04 pm
I believe that this is the only ultrasonic anemometer on the web which has
enough detail to enable it’s actual construction.

I have replied to your email and hope that it will put you on the right track.

39  Community / Exhibition / Gallery / Re: RF link display using the ATtiny85 on: February 04, 2012, 05:37:17 pm
I think you are right it does look like a timing problem.

I,m sure you have the necessary skills to solve your problem.

Make sure you download the data sheet for the 85. It has all the information you will need
to setup the timers.

40  Community / Exhibition / Gallery / Re: Manchester encoding library for RF links. on: January 22, 2012, 07:26:16 pm


This was discovered by mchr.

I wont update my code because mchr has done a great job on improving the library.

I would now direct anyone using this code to use his modifications:

41  Community / Exhibition / Gallery / Re: Manchester encoding library for RF links. on: January 20, 2012, 12:48:07 am
If you are thinking of using the  ATTiny85 as the transmitter checkout:

This is an excellent article by mchr3k. He uses the 85 as the Tx with this manchester library.
42  Community / Exhibition / Gallery / Re: Manchester encoding library for RF links. on: January 11, 2012, 08:28:23 pm
It sounds as though something is being sent by the 85.

How do you program the 85, I use:,59968.0.html

There is a pdf  which describes how to set the fuse bits.

When you dump lfuse you should get  E2  this gives:

8 Mhz on the internal clock.

I mention this because the example sends data every 0.1 sec not 1 sec.

Keep at it!
43  Community / Exhibition / Gallery / Re: Manchester encoding library for RF links. on: January 09, 2012, 04:51:11 pm
When we get all 0's it could be anything.

My first guess would be hardware.

What rf devices are you using?

Do you have access to a CRO to see if data is going to the Tx or being received at the Rx.

Without lots more information I cannot be more explicit.

44  Community / Exhibition / Gallery / Re: RF link display using the ATtiny85 on: January 06, 2012, 03:52:21 pm
You are right I did not modify virtual wire to use the 85 as the Tx.

I wrote another library to use the 85 as Tx or Rx.,63755.0.html
45  Community / Exhibition / Gallery / Re: Manchester encoding library for RF links. on: December 16, 2011, 11:17:48 pm
The cores goes in:


The manchester library goes in:


The examples should then compile.
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