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1  Using Arduino / Project Guidance / Re: Disdrometer to measure rain and hail, limit voltage on: July 22, 2014, 06:23:24 pm
What you need to add to the output of the amp is called a CLAMPING circuit, this can be as simple as a resistor and a zener diode.
Google 'voltage clamping circuit' and see what you get.

Thanks Tom

The clamping circuit is what I was after just not sure of its name.

Cheers

Chris
2  Using Arduino / Project Guidance / Disdrometer to measure rain and hail, limit voltage on: July 21, 2014, 10:02:52 pm
Hi

I am wanting to create a simple circuit using a Piezo Electric element to generate a voltage when it detects that it is raining or hailing outside. This will be interfaced to an Arduino and PC at a later stage.

The piezo element can product a positive and negative voltage when it picks up a vibration so I am thinking of using a Schottky Diode to rectify the signal so I only get positive voltage values.

The next issue is I am unsure of the maximum voltage that could be induced in the piezo element especially if I amplify the output voltage a little bit. Sometimes hail is very very heavy and may produce a larger voltage than I am expecting.

So my question is:

I want a limit the voltage to a maximum of 5v so even if the piezo + amplifier produced 7v I just want to truncate it at 5v, but the voltage < 5v is left to be what ever it is.

in software c# it would be something like below but I am unsure of the terminology to use when searching and hence my post here.

int Value = (Value > 5 ? 5 : Value)

Any help appreciated.

Chris
3  Using Arduino / Project Guidance / Re: Help reading backscatter light from led using CDS LDR photoresistor. on: July 02, 2014, 06:00:09 pm
Looks like the original airharp creator "Peter DeSimone" tried a kickstarter campain but it failed to meet its funding in April this year.
https://www.kickstarter.com/projects/lyratron/airharp-ultrasonic-digital-autoharp

There is a web site at http://www.airharp.com/  with schematics and source code and the ability to buy complete units.

There is also an instructable about building it.
http://www.instructables.com/id/How-to-build-an-AirHarp/

Chris
4  Using Arduino / Project Guidance / Re: DS1302 RTC not working on Mega2560 but fine on UNO on: March 01, 2014, 02:59:29 pm
looks like my bad - I had the pins connected as follows

// CE pin    -> Arduino Digital 11
// I/O pin   -> Arduino Digital 12
// SCLK pin  -> Arduino Digital 13

I removed a shield and put it onto pins 2,3,4 and it worked on the mega 2560

So I moved to

// CE pin    -> Arduino Digital 43
// I/O pin   -> Arduino Digital 41
// SCLK pin  -> Arduino Digital 39

And it still works...

so I moved to

// CE pin    -> Arduino Digital 10
// I/O pin   -> Arduino Digital 12
// SCLK pin  -> Arduino Digital 12

and it works, so pin 13 must be causing an issue since it is connected to the onboard led....

Chris
5  Using Arduino / Project Guidance / DS1302 RTC not working on Mega2560 but fine on UNO on: March 01, 2014, 02:37:38 pm
Hi

I am using a DS1302 RTC board and am trying to use it on an AT MEGA without success.



The board works fine when connected to an UNO board, using the library from

http://www.henningkarlsen.com/electronics/library.php?id=5

But on an at mega it returns garbage data and setting the clock does not work.

Same code on an UNO works fine.

The library says it is compatible with Mega 2560...

Any ideas on where to look to resolve this issue?

Chris
6  Using Arduino / Installation & Troubleshooting / Re: ATMega2560 - Unable to reprogram, how to clear memory? on: February 24, 2014, 12:31:09 am
I tried the loopback from http://forum.arduino.cc/index.php?topic=73748.0 and it worked fine.

I tried to do a bootloader via the ICSP port form a UNO to the 2560 and it failed with a verify failure.

I then tried to upload the blink using the UNO to the 2560 and it said it worked.

But it now does even less. No blink and still fails to upload using a normal arduino upload.

Chris
7  Using Arduino / Installation & Troubleshooting / Re: ATMega2560 - Unable to reprogram, how to clear memory? on: February 23, 2014, 11:44:09 pm
Is there some low level way to remove the current program?

How about re applying the boot loader? Does that clear memory?

Would that even work?

chris
8  Using Arduino / Installation & Troubleshooting / Re: ATMega2560 - Unable to reprogram, how to clear memory? on: February 23, 2014, 11:37:49 pm
Under File:Preferences, turn on verbose outputs.

Press &  hold the reset button, start the download.
When the IDE shows "Compiled xxx of 128xxx bytes" (or similar) release the reset button.
May take a few tries to get the timing right.
Try downloading a simple sketch like Blink so that you are not blasting a ton of stuff out of the serial port.

Are you meaning both Compile + Upload?

Or just compile?

I am trying no luck yet.

It either uploads really quickly and then shows verify errors. Or a message about uploading and then the following

avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: stk500v2_getsync(): timeout communicating with programmer
avrdude: stk500v2_command(): failed miserably to execute command 0x10
avrdude: initialization failed, rc=-1
         Double check connections and try again, or use -F to override
         this check.

Chris
9  Using Arduino / Installation & Troubleshooting / ATMega2560 - Unable to reprogram, how to clear memory? on: February 23, 2014, 06:52:02 pm
I was working on a sketch this morning and I was dealing with pointers and callbacks and something obviously went wrong as the Arduino 2560 is continually looping after about 1 second. My script had a delay of 1000ms before it was trying to do some extra work and then not long later it starts again from the start (I assume it is rebooting).

I can see the output in the serial monitor so it is basically working, but then the code restarts and it does this forever.

I can not upload a new sketch as it fails with a verifiy error after the upload

Binary sketch size: 1,632 bytes (of a 258,048 byte maximum)
avrdude: verification error, first mismatch at byte 0x0000
         0x01 != 0x14
avrdude: verification error; content mismatch

I assume it is rebooting/resetting during the upload or something?

Is there any way to get this device back? I have no idea how to proceed.

Chris smiley-cry
10  Using Arduino / General Electronics / Re: Determing Turn Count on a Current Transformer on: February 05, 2014, 08:36:21 pm
I have put the formula I am using into a google spreadsheet.

It calculates the Ideal Burden resister and also allows you to use another value and then compute the current and power. Simple but it was what I was looking for.

May be useful for someone else in the future.

https://docs.google.com/spreadsheet/ccc?key=0AsCVD1YPwixbdGpnOE96Nm1Jc2FMV2x6SDNOVWtwd1E&usp=sharing

Chris
11  Using Arduino / General Electronics / Re: Determing Turn Count on a Current Transformer on: February 05, 2014, 08:26:17 pm
With a shunt resistor in place you can measure the current with a voltmeter instead which
is easier.

I take it a shunt resister could be considered a burden resister as well?

Chris
12  Using Arduino / General Electronics / Determing Turn Count on a Current Transformer on: February 05, 2014, 05:25:49 pm
I have a current transformer that I bought on EBAY as part of a small voltage+current meter.

Basically one of these: http://www.ebay.com/itm/AC-80-300V-100A-Blue-Lcd-Digital-Dual-Panel-Volt-Amp-MeterCurrent-Transformer-/251338181819#ht_1980wt_1399

It does not specify what the CT is rated at.

From another post I found a formula and would like to know if my calculations are correct.

Quote
You could also calculate it if you had the input current and output current.  If the output current at 20A was 10 mA (0.01 A) you would divide 20 by 0.01 to get 2000.

So I live in New Zealand and I am using a FAN heater as a test bed at 1/2 heat. I believe the fan heater is 2000w at full power, and 1000w at 1/2 power.

Current AC Voltage : 233v AC
Fan Heat set to 1000w which is 1000 / 233 = 4.2918 AMPS

Now cabling one of the AC cables though the CT it is producing 13.84 milliamps of AC current on my digital multimeter.

So from what I believe from the above formula :

4.2918 / 0.01384 = 310.10 turns.

So it is probably a 300:1 CT ?

Chris
13  Using Arduino / Project Guidance / Re: Cheap connectors to mount cat 5 cables or similar on: December 31, 2013, 02:56:33 am
Hi

I ended up buying those products I posted about on my original post.

Yes the problem was the panel mounting not the connector.

On Ebay there is very little actual useful panel mounting products. Most are PCB based which is fine if you can create your own board and box.

Chris
14  Using Arduino / Project Guidance / Cheap connectors to mount cat 5 cables or similar on: December 30, 2013, 05:14:16 pm
I have a project with a small arduino nano and I want to put it into a small plastic box. It will run from USB port and it will allow 4-8 Dallas ds18B20 one wire temperature sensors each on its own cat 5 cable. At the moment I am only allowing 4 connectors since each connector will go to a seperate IO port. I know I can put multiple on a single cable but cable length can be a factor then.

Now the cables connecting to the Ds18B20 is a cheap CAT 5E ethernet cable.

I would want  to have a simple connector to connect each sensor - 3 wires each as they are running in standard mode (not parasitic power).

This seems to be the problem for me as I can find plugs like 3.5mm audio plugs but panel mounted sockets not so simply. I could use RJ45 or RJ11 but again no cheap panel mounts to mount to the plastic case.

I have really only been looking on EBAY as everything in New Zealand is expensive if I look at local electronic stores.

Any ideas of what is a good way to mount this type of setup?

At the moment I am thinking of buying a few of these and cutting the end off so they hang free of the box - cheap at $1 each

http://www.ebay.com/itm/3-5mm-Audio-Earphone-Headphone-Splitter-Cable-Adapter-Jack-Male-to-2-Female-TE-/121199901571?pt=US_Audio_Cables_Adapters&hash=item1c3813bb83#ht_2565wt_1362

and these connectors  10 for $3

http://www.ebay.com/itm/DIY10pcs-3-5MM-Stereo-Audio-Jack-Male-Plug-Adapter-Connector-Solder-Cord-For-MP3-/181124028867?pt=US_Surveillance_Cables_Adapters_Connectors&hash=item2a2bd559c3#ht_3417wt_1124

Any better ideas?

Cheers

Chris
15  Using Arduino / Microcontrollers / Re: How to support Serial Communications on a bare bones arduino on: September 22, 2013, 07:05:31 pm
Thanks Paul

Just what I needed - I forgot about the twist in the RX/TX as well..

Cheers

Chris
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