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31  Using Arduino / Sensors / Re: Simple trip line motion sensor on: December 10, 2013, 09:10:59 pm
If the PIR sensor is too broad, you can (a) remove the fresnel 'bubble' lens covering it and/or fashion a tube/funnel for it to look through with a length and diameter than gives you the sort of 'beam' control you want.  That may be of limited success as a really narrow beam may defeat the sensors ability to detect motion [just my speculation].
32  Using Arduino / Sensors / Re: DS18S20 temp sensor won't go below 32F on: December 10, 2013, 09:05:09 pm
You're probably just not reading the data stream correctly.  Have you read or similar description of what the sensor outputs (see page 4 in the link)?
33  Using Arduino / Programming Questions / Re: GSM on: December 10, 2013, 09:02:06 pm
You need to establish values for x and y, of course.  Whatever that entails, checking the value of the millis() function or some external input (switch closure changing the signal level on one of the digital inputs?)

AT+CMGS is a 'AT command' which is the typical method of controlling modems, such as the GSM unit you have.  The command consists of the command itself, the number to dial, a newline, the SMS text to send and a command terminator (which you do not seem to include).  a ctl-Z, esc or some such character is sent to tell the modem 'that's the entire message, now send it'.

34  Using Arduino / Programming Questions / Re: byte mirror code don't work on: December 06, 2013, 02:56:04 pm
See how simply robtillaart answered this question in a previous thread:
35  Using Arduino / Project Guidance / Delving into GSM/GPRS on: December 06, 2013, 01:11:37 pm
I bought a GSM/GPRS board today.  Seems like interfacing to Arduino will be pretty simple via serial port. 

However, the means for obtaining a SIM for it is not clear nor is the most cost effective route to go.  I intend to issue periodic, infrequent SMS or small email messages (this is an alarm warning notification application so there better not be very many!).

Anyone in the US been through the search for cheap, low data volume airtime sources?

Seems like T-Mobile *might* get me into a roughly $20/year payment pattern with their offerings, based on some reading I've done.  But that sounds *really* cheap and so I'm not that confident the source was accurate.  In that scenario, you buy a by-the-minute plan, fork over $100 to get into their 'gold' level of service and then switch to a pay as you go.  The $100 doesn't expire for a whole year and you need to do a refresh of $10 a couple times a year.  Yeah, the 'entry fee' is a bit salty.

If that is true, then great.  But if not, what have the rest of you found cost effective?
36  Using Arduino / Networking, Protocols, and Devices / Re: nrf24l01 radios + RF24 library + Ethernet shield do not work together on: December 05, 2013, 05:41:39 pm
I have added a 10uf electrolytic across the 3.3v input to the nRF24l01, which cured my problem using those two devices together.  It would work *some* but eventually would always quit.  They just seem to be very delicate.
37  Using Arduino / Project Guidance / Re: Arduino Cell phone repeater / signal booster on: December 05, 2013, 01:07:36 pm
Boy I just love it when your looking for help on here all you find is assholes. I apologize for us nerds that have a lack of social and communication skills. I spent half my time in school keeping them from getting beat up..and still  nothing in return
 First thing would be to figure out what frequency your phone is running/transmitting and receiving. this can be done with a google search of your carrier. second is to do as I am doing and figure out how to build an amplifier for that general frq.(I need 1900mhz)  Hope this helps you I could do for now...still learning what all can be done with this amazing little board.

Not sure if that was directed at me, but it really IS a serious matter to be aware of and steer clear of.  The FCC is rather mercenary and heartless when it comes to infringing on their spectrum allocations.
38  Using Arduino / Project Guidance / Re: Arduino Cell phone repeater / signal booster on: December 05, 2013, 12:52:56 pm
Main problem with this project idea is you would need formal 'type acceptance' (at least that's what it is called in the US) from the government's RF spectrum manager (again, in the US that's the FCC).  You are talking about transmitting in regulate spectrum.

If the FCC takes notice of your transmitter, they can and usually do issue stiff fines (a Notice of Forfeiture) in the $10,000 range.

The other RF devices you see used with Arduinos or by hobbists in general are in specifically-allocated spectrum for general unlicensed operation.
39  Using Arduino / General Electronics / Re: Single-wire 24VAC input to Arduino on: December 05, 2013, 07:50:05 am
Another way to visual it is fully turning on a faucet and turning it off rapidly.  You get what they call 'water hammer'.  That's the water rushing through the pipe and inertia producing a force that briefly exceeds the nominal water pressure.
40  Using Arduino / General Electronics / Re: Single-wire 24VAC input to Arduino on: December 04, 2013, 07:48:18 pm
The convention for HVAC signalling is (most of the time):

RED - Power (one side of the isolation transformer)
BLU - Common (other side of the isolation transformer
YEL -  Call for cooling (you have none)
WHT - Call for heat (the zone valve)
GRN - Fan relay (but you have no fan)


The MID400 senses the 24VAC, which is switched on/off in the thermostat onto YEL, WHT and GRN wires for the corresponding signal back to the heating plant.

So  an MID400 could sense between BLU and YEL, BLU and WHT, BLU and GRN (or BLU and RED to detect whether the system is switched off completely)

And yes, you could utilize the spare green wire you have to be the common lead.  Presently you have (irrespective of what colors are in your bundle) WHT and RED connected to your thermostat.  RED going to the thermostat and WHT returning the call for heat.  So you could make the green wire BLU and a MID400 would connect to BLU and WHT.

And I just realized I *assumed* your zone valves are binary on/off devices and not variable-flow, which is a whole 'nuther thing.
41  Using Arduino / General Electronics / Re: Single-wire 24VAC input to Arduino on: December 04, 2013, 06:42:26 pm
John -- that IC won't work.  You don't have AC hot and neutral at the thermostat, you only have hot.  You can't ever directly measure an isolated voltage with only one wire.  The best you can hope for is inductive, but 24vAC control lines are very low-current.  You would have to use a sensitive inductive meter...

Although I would not connect it at the thermostat myself but rather at the furnace, that should be possible anyway.  It is normal to have a 5 or 6 wire 'thermostat cable' in place even when not all conductors are used.  If not a blue 'ground' (actually just one side of the isolation transformer) already there and connected (in mine it is) there's most likely a conductor you can connect up.  That should be true of any house built since the 60's and certainly one that has A/C (OP didn't mention that though and I realize zone valves are a radiant hot water component).

I had to resort to that when I recently added a 24VAC-powered wi-fi thermostat and needed an always-hot 'C' wire as they call it -- I used one of the unused wires in the bundle.
42  Using Arduino / Project Guidance / Re: Yes all i keep getting is Board at COM1 is not available on: December 04, 2013, 05:27:39 pm
Look in the Arduino/drivers folder on your computer (wherever it was you installed the Arduino IDE software).  Install the USB driver in there and you will be able to connect with your Arduino board.
43  Using Arduino / Sensors / Re: Connect a sensor chip on: December 04, 2013, 05:12:11 pm
The most practical way to connect a surface-mount IC to an Arduino is to buy it mounted on a breakout board:

But is possible connect without it. Connecting the capacitators on the breadboard an connect the chip with a cable.

The determinator is whether the pins on the chip match up with the board's contact matrix (it probably won't).  It will be much simpler to buy a prototyping board like and as Johnwasser alluded, mount a breakout board with the chip on it.  Then attach to the Arduino.
44  Using Arduino / General Electronics / Re: SMD Soldering Training PCBs on: December 04, 2013, 05:03:26 pm

I do NOT miss the days of RubyLith films and exacto knives OR the spray resist and ferric chloride.  Praise be the PCB jobbers.
45  Using Arduino / General Electronics / Re: Single-wire 24VAC input to Arduino on: December 04, 2013, 04:57:13 pm
I used some Fairchild MID400 chips, which are designed exactly for this kind of application.  Works great!  They are opto-isolators and can handle up to around 250 VAC on the input side, as I recall.
That looks great! Probably means ordering it, unless the local (small) RadioShack has them or something equivalent. Which sucks, because I was hoping to be logging data by the weekend (and shipping things to Alaska takes time). Can this be hooked up in series with the line to the zone valve, or do I have to do this in parallel and still have the issue of figuring out how to ground it?

You would connect to the switched side of the thermostat, so the MID400 'sees' 24V whenever the thermostat completes its circuit.  In effect, you are illuminating an LED inside the MID400 and this causes the output side's photosensor to switch the 5V signal.
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