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1  Using Arduino / General Electronics / Re: Circuit need: Cutting a wire gives HIGH signal - 12V supply on: May 13, 2013, 04:03:11 pm
Sorry about the spamming here..
No, that only worked because the battery had drained sufficiently for the triggervoltage on base to drop below 1,5V.
With a fully charged battery, it became 1,5V. Time to break out the spreadsheet again..  56K and 3,3K, perhaps?
2  Using Arduino / General Electronics / Re: Circuit need: Cutting a wire gives HIGH signal - 12V supply on: May 13, 2013, 02:28:45 pm
Well, that img-link sure worked well..

It's at:  https://www.dropbox.com/s/6eqeag4pm46vojy/circuit.jpg

3  Using Arduino / General Electronics / Re: Circuit need: Cutting a wire gives HIGH signal - 12V supply on: May 13, 2013, 02:20:10 pm
Hi, and thanks for your patience.
The input I am using on the device is actually meant to be connected directly to the ignition of a car - to sense that someone has turned the ignition on.
It is probably well protected on the inside - optocoupler / fuse etc. I measure the 56K to ground.

And: I think we may have this working now. I added a BC548 transistor, and fed the signal into it, thus:


The voltages listed are with the circuit closed, the voltages in (brackets) are with the "wire cut".

This approach gives consistent operation of the device, with a current drain at rest at < 0,1mA

Do you see any flaws, if not we may mark this as [Solved] :-)
4  Using Arduino / General Electronics / Re: Circuit need: Cutting a wire gives HIGH signal - 12V supply on: May 12, 2013, 02:57:43 pm
Thanks very, we're getting somewhere..
I tried R1=R2=4,7K and got 6V at the measuring point.
With R1=47K I got ~1,2V at the measuring point with wires uncut and ~7V with them cut.
However, the device has an internat 56K resistor, and wih the device attached I got ~2,5V at the measuring point.
I've played with 22K and 33K as R1, but I am still struggling with getting consistent operation. If I attach the device straight to 12V, I get good, solid operation.
Methinks I may have to add a transistor/relay to switch 12V based on the potential from the measuring point?

5  Using Arduino / General Electronics / Re: Circuit need: Cutting a wire gives HIGH signal - 12V supply on: May 11, 2013, 07:08:55 pm
Use 2 wires.
both are tied together at your motor.
The other ends are at the two resistors.
Have your sensor at the resistor that is tied to 12 volts.
At the moment the wires are intact, you'll have a low voltage.
After cutting the cable, (or only 1 wire), the resistor will pull it up to 12 volts, and your alarm will be activated.
You would have to find out what pulldown resistor is in the unit, so you can use a resistor small enough to override that, and large enough to not drain your battery too much.

I'm sorry, I didn't quite get this, could you do a quick drawing?

All other replies in this thread are also much appreciated, and led me to understand that I haven't been sufficiently clear.
1) marking/blocking/tagging the motor won't help. It may be stolen in Norway, and will in that case be resold in a country our conventions of resale value do not apply.
2) I'm not planning on using any existing wires, the plan was to run a wire back/forth to the motor (2-lead cable connected at the end) and use the cutting of this pair as the signal
3) they will most probably simply snip off all wires & cables to the engine, lift it off and be off with it in 10 minutes. I'm not expecting them to ponder much or look hard for the transmitter.
4) actually, I won't be using an arduino for this as I found a device on ebay that combines GSM+GPS+Acellerometer+magnetic compass that will send sms's through a well-developed protocol, both easier & cheaper than I could cobble together an Ard+gsm+gps+accel+gyro+magnetometer+charger+battery

Please keep the ideas comimg :-)
6  Using Arduino / General Electronics / Circuit need: Cutting a wire gives HIGH signal - 12V supply on: May 11, 2013, 06:59:07 am
Hi,
I have a device that will trigger on a +3V to +45V signal, and send an SMS text message. The application is a boat & motor alarm/tracker.
I would like to place a wire going from the boat to the outboard motor.
If this wire is cut (they normally just cut off all wires/cables to save time), someone is stealing my motor.

My problem is to turn this "the wire has been cut"-signal into a +3V to +45V signal for the device.
To complicate matters, I have +12V readily available, but no other voltages.
I require minimal power consumption while the device is in standby.

A voltage divider + a logic NOT gate seems like a good starting point, but I'm concerned about getting a good signal when the input goes from HIGH (connected) to "float" (not connected, not even to ground).

Better ideas, please? :-)
7  Using Arduino / Project Guidance / Re: PTP for Video Capture on Canon camera? on: November 23, 2012, 01:34:36 pm
Well, Mickey..
In return for jogging my memory, I'll gratify you with an answer.

The sports event is none of your business, but there are no restrictions on photography/video, as is common in Europe, those restrictions are a US exclusive.

One of my daughters competes at a national level in this sport. The best spot is center stage (center mat), but unfortunately that's where the judges are sitting.

So a camera with a 14mm, placed in front of the judges, below their line of sight, is the sweet spot.

Which is why a visual indicator is not a good idea, it would distract the judges. Hence the radio need & the need for distance. 'Cause I'm busy taking pictures from the next-best-spot.
8  Using Arduino / Project Guidance / Re: PTP for Video Capture on Canon camera? on: November 22, 2012, 09:20:47 pm
Thanks, not bad :-) You triggered me to remember that Magic Lantern supports remapping of the "REC" key. I've remapped it to the "Shutter Half-press", and with a wireless remote I can start video with a key-press.

FYI - I'm using a Canon 550D, and the gig is to remotely shoot video of a sports event, from a location where photographers are not allowed.
The plan is to walk up there in a break, deposit tripod & camera, and then start/stop the video from a different location.

I still have two problems, though..:
1) The solution is not based on an Arduino ;-)
2) I don't have a visual clue from 50 paces that the video is on & the camera is recording.

My plan was to use an Arduino + USB shield to start video, and keep a 2nd Arduino wirelessly updated with the status of the camera.
Hm. I'll bet turning on video creates an identifiable EOSEvent that I can parse & send. Hm. Not as elegant as Plan A, but still. Hm.
9  Using Arduino / Project Guidance / Re: PTP for Video Capture on Canon camera? on: November 21, 2012, 04:38:02 pm
Yes, I found that, but I need the source for that HEX-code :-)

I'm not going to use Bluetooth & Android, but rather a second Arduino to do the triggering, with a wireless radio between.

Basically, "all" I need is the command to do "eos.start_capture_video" and of course _stop_. (it's probably not that simple, but you get the idea..)

Failing that, a link to the programmers guide..
I can't find the video options in the ability pages for the EOS cameras, and assume they are within the "vendor specific".
10  Using Arduino / Project Guidance / Re: Some networking fun: 28 arduinos linked in a network on: November 21, 2012, 10:41:08 am
I've been thinking of the network control here, and the cost of the devices. Ethernet simplifies some things, but is expensive, and still leaves you with a bit of programming to do.

Can the nodes be polled, or do they react to an event to transmit data?

If they can be polled, I believe I'd :
* Buy $4 RS-485 boards off eBay
* Give each node a node-id.
* Put each node in listen-mode (in RS485 terms)
* Use EasyTransfer for the transfers back & forth, as this simplifies programming, adds checksums etc. It also simplifies management of data types, you can send an arbitrary struct.
* Have the Master send a package to each node in turn, then have Master go to "listen mode".
* A node having received "his" package prepares his return data, enables transmit mode, sends data, and goes to "listen" again.
* The master receives data, handles this in an appropriate way, enables transmit, and repeats.
* The master needs to handle a time-out
* You might get electrical problems on the RS485 bus if a node gets stuck in transmit enable mode.

btw: the avrdude issue usually means that you have something hogging the serial port on the Arduino - a device is hooked up to TX/RX and conflicts with the IDE trying to use the same pins.
11  Using Arduino / Project Guidance / PTP for Video Capture on Canon camera? on: November 21, 2012, 09:58:35 am

I’ve used the USB shield & the PTP EOS (https://github.com/felis/PTP_2.0) library to capture images with my Canon camera.

Now I have a need to start / stop video recording with the same setup.

I realise this is not included in the library yet, but does anyone have any clues to how this may be implemented?

I see http://dslrsystems.com/ have achieved this, but the code is not available from Google code anymore, it’s only available as a .HEX file download.

Any clues?
12  Using Arduino / General Electronics / Re: Arduino dB meter / noise-level meter - circuit? on: August 16, 2012, 04:08:21 pm
Hi guys,

Thanks so far. I've added a 100uF across Vin/GND, changed the input cap to 1uF and replaced the diode.

My multimeter says about "2V" is coming out of LM386 leg 5. My "scope" is a soundcard probe with Zeitnitz Scope, and I'm not confident about it's Vpp metering. However, I temporarily replaced the diode with a LED, and got light according to soundlevel, so we're not totally off scale.

I tried connecting the anode of the diode to 5,4V (having disconnected the diode from the lm386 first), and got 4.9V dc on C2 and R2.

I'm still roughly getting the same results.

I get to play with this again on Sunday. Will rip everything apart and build from scratch then, by now I'm seeing ghost in broad daylight. Thanks, guys.
13  Using Arduino / General Electronics / Re: Arduino dB meter / noise-level meter - circuit? on: August 16, 2012, 06:38:14 am
Thanks, guys.

Update:
* The "nothing after the diode" means the scope registers nada here. I haven't actually attached the Arduino yet.
* The diode is the right way around, and looks good according to my multimeter.

What I hear is that the design is basically sound, and that we need some bug-fixing/tweaking. That's progress, too.

What I'll try, according to your suggestions is:
1) Add a 100uF across Vin/GND, that's the largest I have (actually I tried this, but it dampened the output signal from the LM386, so I removed it). But it goes back in.
2) Change the input cap to 1uF
3) Replace the diode, just in case

Pito: Could I bother you with a further expansion of t=k*R*C? I assume that R is resistance in Ohms, the C capacitance in F, and t the time in s? But k?

Thanks in advance.
14  Using Arduino / General Electronics / Arduino dB meter / noise-level meter - circuit? on: August 16, 2012, 01:53:05 am
Hi,

See http://wiring.org.co/learning/basics/microphone.html.

I have this up on a breadboard, with a 1N4001 diode, according to the diagram, not the drawing (misplaced diode).
I have omitted the 1000uF cap across Vin/GND, didn't have one.

I'm getting a nice amplified signal on my scope from pin 5 of the LM386, but nothing after the diode.

Ideas? Have anyone tried this? Which diode did the designer actually have in mind? Do I need to change the values of the caps/resistors?

Do you have an alternate design? I have LM386's available + a few handfuls of transistors. And there's a bit of urgency, so waiting for delivery of components is undesirable.

If we can't get the circuit to work, do you have an idea to do the integration/envelope in SW on the Arduino?

The application is "how loud is it, on an arbitrary scale, right now". I need to catch peaks of ~100ms duration.
15  Using Arduino / Programming Questions / Re: How to send an integer value through serial port? (Arduino to Pc) on: July 28, 2012, 06:52:12 pm
Look at EasyTransfer - it's a library that sends any data across serial, with CRC. It's simple to implement, and in the basic serial mode, has good example programs.
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