Data recorder via gsm or wifi

I'm designing a project for recording different sensor data such as gases, dust, uv, temperature etc. I would then post this data to a Web server/db via wifi or GPRS.

I'm wondering about pin availability. The wifi shield for arduino seems to take up pins 10,11,12 & 13. But I can't find how many pins the GPRS shield would use up?

Aside from the disadvantage of data-sending being more expensive via GPRS, which shield would use up fewer pins, thus freeing them up for use with the sensors?

Which gprs shield? Most of these use serial connection, so 2 pins. I do a lot of data logging and telemetry. I use mega for more pins and memory. If you log data, you need sd card for local storage. With wifi, you need cellular hotspot, not necessarily cheaper than gprs.

I don't need memory on board if I'm going to be posting to the Internet. Once I post I free up on board memory.

Marciokoko:
I don't need memory on board if I'm going to be posting to the Internet.

Words you will surely regret.

The on-board memory isn't really for the data anyway, that's what the SD is for, the memory is more for the programming space and, if you buy a Uno, you are likely to regret that too..

I meant the SD card memory.

Please enlighten me, seriously, why would I regret it if I'm planning to post everything and not store it?

BTW, I already have an Uno so there is nothing I can do about that. It was the first board I got. I do also have a Mega and I'm thinking about a yun just to avoid a clunky wifi or GPRS shield.

There are degrees of regret which depend rather on how serious you are about what you are doing. You appear to have quite touching faith in your communications, but be assured that they can fail. If you are not serious, I guess it doesn't matter. If you are serious, $5 invested in an SD card might look like a rather good idea.

Marciokoko:
I meant the SD card memory.

Please enlighten me, seriously, why would I regret it if I'm planning to post everything and not store it?

BTW, I already have an Uno so there is nothing I can do about that. It was the first board I got. I do also have a Mega and I'm thinking about a yun just to avoid a clunky wifi or GPRS shield.

Nick has explained it well enough already. It is typical for the internet generation to assume the internet is like air, i.e. available at every moment. There is not a single service, home or business that has a 100% internet connectivity. Even if you do have connectivity, your server may be down thus not receiving data. If you are OK losing data when your internet is down, of course you can do without an SD card. I asked because I didn't know how serious you are with logging your data.

Yun is a weak linux computer with some mcu for I/O. There is a lot less support for Yun than for regular arduino with wifi hardware. Plus, it is expensive and didn't I say it is weak? Depending on your comfort level with linux and some script programming or Python, you may be better off with a raspberry pi that handles wifi networking and arduino that handles sensors. Posting to a server can be done with one line of script using curl. The overall cost is also lower this way. The arduino wifi shield is about $90 each so is a Yun. A raspberry pi 2B + wifi dongle is at most $45 and you get a real computer (1GHz quad core 1GB RAM)!

OK. I'll get the SD card. You're right of course about the connectivity issue. So the best design would be to store to the SD card and upload in batches?

Marciokoko:
OK. I'll get the SD card. You're right of course about the connectivity issue. So the best design would be to store to the SD card and upload in batches?

I think so. It could take arduino wifi shield a good amount of time (seconds or half a minute) to get one transmission to a server using DNS resolution. If you send in batches, it reduces your overhead time. How frequently do you generate data and how frequently do you want to see the data online. What server are you planning on using?

If it were still 2014, I would recommend arduino wireless sd shield (official) and digi xbee wifi module. It's about half the price of arduino wifi shield (official), if you want to use arduino instead of raspberry pi. But something screwed up at the end of 2014 and the official shields come with crappy voltage regulators. They don't work with xbee wifi modules anymore.

There is no set sampling time. I think it could range between 20 to 30 minutes.

I'll post to a private server using php to store in a myself database.

At this rate it is alright to not bundle data for posting. Just make sure your private server won't require secure http connection. Arduino wifi or digi's xbee wifi modules can't do encryption. At the moment digi's xbee wifi module can only do GET but not post. Arduino wifi shield can do both.

liudr:
Yun is a weak linux computer with some mcu for I/O. There is a lot less support for Yun than for regular arduino with wifi hardware. Plus, it is expensive and didn't I say it is weak?

It is weak compared to the PC I am typing on, but it is very powerful compared to an Uno, Mega or Leonardo.

And I think the combined cost of an Uno and a WiFi shield is much the same as a Yun.

See this Program on PC deploy on Yun Thread.

...R

I was saying arduino with raspberry pi 2b. That combo with s WiFi dongle is about $65. Rip 2b has quad core 1Gb processor with 1GB memory and runs raspbian etc. You can also program on a pc and deploy on it. Yun is too limited. A YUN 2 would be nice. More memory and runs more software. But I guess simple data logging is a good fit for YUN.

liudr:
Rip 2b has quad core 1Gb processor with 1GB memory and runs raspbian etc.

Yes, the RPi is more powerful than a Yun - but if the Yun is powerful enough and will be permanently dedicated to one task the extra capabilities have no value.

The reason I haven't bought an RPi is because I don't have a TV. I can "talk" to my Yun with my PC "out-of-the-box"

I do agree the Yun is expensive. I can't see why it costs more than a Pi - Arduino greed, I suspect.

...R

I agree. I need yun's built in wifi capability. Other than that I just need some space to temporarily hold backup data until it it wifi-ed off the board into the cloud.

I know little about Arduino (started with it about 2 weeks ago) so I know 0 about R-pi except that it is more of a full fledged computer rather than a, uh, whatever an Arduino is

The Yun includes a microSD card slot which could be used to store data.

...R

Go with a Yun then. BTW, you don't need TV for rpi. If you have a PC monitor, you can use it for initial setup. Then just log in to it remotely. It's linux.

liudr:
If you have a PC monitor, you can use it for initial setup.

Nope. Only a laptop (or two).

...R

Then you have to get an image that is already set up. If you have a public library, I bet you can find a monitor to use for 10 minutes.

liudr:
Then you have to get an image that is already set up. If you have a public library, I bet you can find a monitor to use for 10 minutes.

Simpler not to bother with an RPi :slight_smile:

Until such time as they figure things out and include the appropriate software by default.

...R