Will this project combination work?

Hello,

I have been doing some research on combining three products. I would like to put the following 3 things together.

First I checked if there are any conflicting pins,

Arduino GSM Shield uses pins 2(gsm rx),3(gsm tx), and 7(modem reset).
Adafruit TFT 2.8" TFT Touch Screen uses pins 9-13(display), 8(touch), and 4(sdcard).

So I should be good with the 2.8" screen in the pin out department.

Next, I check the requirements to power each device.

Arduino GSM Shield overview page says that it is not recommend to use USB power as it is not sufficient enough to handle peak usage. Peak usage can draw up to 2A. It is recommend to use a power supply that can prove between 700mA and 1000mA.

Adafruit TFT 2.8" TFT Touch Screen description said "Onboard 3.3V @ 300mA LDO regulator, current draw depends on usage but is about 100mA for the display and touchscreen". Little confusded here but I think it uses 100mA, please correct me if I am wrong.

And then my thoughts on the physical build are based on a video I saw on Arduino Youtube page.

If you look at the screen shot of the video above, you can see that the presenter connected the Uno Board underneath the GSM Board... and still has more pins available on the other side of the GSM shield. I was wondering if it is possible to mount the TFT LCD from above on the other side of the GSM shield? Kinda of like a sandwhiching them all together then connecting it to a power supply.

Now I tried to google stuff like "How to combine Arduino Boards", "Stack Arduino Boards", etc. But Couldn't find anything. My guess is that you unsolder the current pins on it and replace it wih some sort of a double sided pin.

My questions and concerns, which brings me here. Hopefully someone with more knowledge on the subject could help me out here.

1.) What kind of external power supply will I need?
The GSM required 700-1000mA and LCD requires 100mA. The Uno product overview recommend to use a 7-12V power external power supply. I am un-familier with the measurements so I am not sure what to get for the power supply. Should I be looking for 9-12V? Will that be too much?

2.) Is the sandwich build possible?
I know the Uno and GSM would attach ok, but will I be able to attach that touch screen to the other side?

3.) Will the pin out on 3.5" screen be the same as 2.8" screen?
I could not find the pin out like I did on the 2.8" screens product overview, or maybe the terminology used went right over my head. I assume it would be the same, but I would just like to confirm with someone else before I did get it.

Thanks for reading guys, I'm sorry about the long write. I tried to make it a little more visually appealing for your reading pleasures, lol. So any thoughts of this build will work?

OK - some basic points:

Arduino shields have a standard pin layout to match that of the board they are made for. This is nearly always that of the "Uno" board.

The pin headers used on most shields are "pass-through", meaning that you can plug one shield on top of another and the pin connections are passed through all the way to the top. This means that any shield can access any pin. Where there is a conflict of pins, this can be a problem but for a situation like yours you should just be able to stack GSM on the Uno and touchscreen on top of the GSM. Shields like LCDs often are not "pass-through" because if you stack anything on top of it you can't use it.

If they are both Uno shields then the physical pins on the 3.5" shield will match those on the 2.8". Anything else may be different (e.g. which pins it uses and how it communicates). If they are both Adafruit then they are probably compatible in most other ways too.

The final question is power. You want to be able to supply lots of current. You supply power to the Uno, it regulates that down to +5v to power the Uno and the GSM. The touchscreen then regulates that down again to 3.3v for itself. You need around 1000mA for the Uno/GSM and 100mA for the screen (according to your research - I have not checked). This leaves two questions:

Can the Uno generate that much current?

If so, what power supply do you need to provide.

The answer to the second question is easy - at least 1.2A (1200 mA) at 7-12v. Unfortunately, the answer to the first is "maybe"!

The NCP1117 regulator on the Uno is rated to 1A (1000 mA). That means that 1100mA you expect to need is a little more than its rated current. There are three things that you can do about this:

  1. (risky) risk it - you probably have a margin of safety in your estimates so you might be OK. This is not the best plan but it might be OK for testing if you keep your run times low. The reg' has a thermal shutdown so you are more likely to get unreliable operation than you are to burn it out but you do run some risk of that.

  2. (still risky) risk it but be careful - you can help the regulator by, for example, supplying closer to 7v than 12v. The less voltage it needs to drop the less likely the reg' is to overheat. You could also add an external heat-sink to it.

  3. (best but take care) use an external high-current supply. You can, for example, use the 5v line from an old PC power supply. That will be rated around 20-30A and can supply what you need in its sleep. You would attach this direct to the Gnd and +5v pins but be careful not to supply power this way at the same time as you have USB power attached or you could blow your USB port.

Good luck with the project.

Ugi

Slightly off topic, but have you got your Arduino GSM/GPRS shield yet? The only reason I ask is because they are uncommon at the moment. It's not in the store any longer.

Dr_Ugi:

  1. (risky) risk it - you probably have a margin of safety in your estimates so you might be OK. This is not the best plan but it might be OK for testing if you keep your run times low. The reg' has a thermal shutdown so you are more likely to get unreliable operation than you are to burn it out but you do run some risk of that.

  2. (still risky) risk it but be careful - you can help the regulator by, for example, supplying closer to 7v than 12v. The less voltage it needs to drop the less likely the reg' is to overheat. You could also add an external heat-sink to it.

  3. (best but take care) use an external high-current supply. You can, for example, use the 5v line from an old PC power supply. That will be rated around 20-30A and can supply what you need in its sleep. You would attach this direct to the Gnd and +5v pins but be careful not to supply power this way at the same time as you have USB power attached or you could blow your USB port.

Damn, I did not expect this much trouble in the power department. I thought the Arduino Uno would be able to take in the required amount of power and distribute it safely across the boards by default since it had that power jack on it.

I managed to find a "how to" on building an ArduinoPhone. Link

In this "How to" he used something called a "Custom ArduinoPhone Charge Circuit (or Lipo Rider)". The product specs on this read

I also found similar products such as the Adafruit 500, 1000, 500c, and 1000c.

dannable:
Slightly off topic, but have you got your Arduino GSM/GPRS shield yet? The only reason I ask is because they are uncommon at the moment. It's not in the store any longer.

Well that explains why the 'buy' link is broken on the arduino website. I figured I would just be able to get it off amazon or ebay. I just tried looking for the GSM shield and you're right they are hard to find, and a little pricey too if I may add. Was not expecting to pay $120 for it.

Amazon GSM Shield

I can buy the GPRS Shield locally. There is a local RadioShack that's closing down and they are liquidating all merchandise (60-80% off). I just purchased 2 Arduino Micro's and 1 Esplora from them the other day for half off. Last ones. Those were actually my first Arduino boards, loving it. Learned a lot in the past 2 days, this stuff is pretty fun. pushes glasses up with index finger

I saw they had a ton of those GPRS Shields on the shelves. I may go back tomorrow and buy 1 or 2 of them. I didn't know what they were when I first saw them.

I can't seem to find much detail on the GPRS Shield, and I don't see it on arduino website either.

Whats the difference between the GSM Shield and GPRS Shield?

Does the GPRS shield draw less power? The "How to build ArduinoPhone"(link above) uses the GPRS Shield and 400mA booster. If so then this is a better solution for me than the GPS Shield which is way more costly too.

GSM and GPRS are different methods of communicating. GSM is text / SMS, GPRS is 'web', at the risk of over simplifying it! Most shields can handle both.

It's a good shield, it can connect to the network when others fail. But for that sort of money you shouldn't have to bend pins out of the way to use it with certain models of Arduino.

dannable:
GSM and GPRS are different methods of communicating. GSM is text / SMS, GPRS is 'web', at the risk of over simplifying it! Most shields can handle both.

It's a good shield, it can connect to the network when others fail. But for that sort of money you shouldn't have to bend pins out of the way to use it with certain models of Arduino.

But it can still send and receive text messages, it just uses a different protocol? If it is doing it through the 'web' does that mean I need to buy a sim card with web capabilities? I think these cost a little more if I am not mistaken.

I just grabbed one from RadioShack (P.S. Offtopic, RadioShack sale is a scam. They marked the price of the GRSM at 60$ and put a 50% off tag above it...)

I saw the link in your signature and noticed that our boards are a little different. Did you add that antenna or did it come with it? Can I add one? Also my doesn't have two 3.5mm jacks (1xSpeaker 1xMic), it just has one jack and a label with a headset microphone.


Ima read that link in your sig when I get back from work later today and see if I can start playing around with this thing while waiting for other parts to ship.

Ok, that isn't an official Arduino shield. They use the Quectel M10, not the SIM900.

Your version is different to the one I wrote about but the basic principals are the same. Mine is as it came, from a certain well known auction site! The battery holder on yours is (probably) for the real time clock, not stunningly accurate. You can get adapters for the aerial, you need an IPEX To SMA cable to connect the board to an aerial, and then a suitable aerial.

SMS (text) uses GSM. If you want to upload data to a website (for instance) you need GPRS. SIM900 supports both and is quad band, which is more important, it will operate anywhere in the world.

As for the pin usage - sorry, can't help you there!

(Just thought - doesn't that shield use D7 & D8 for comms? Not D2 & D3?)

dannable:
doesn’t that shield use D7 & D8 for comms? Not D2 & D3?)

Damn your right. no work around for that i assume? If i did it on breadboard could i move the pins?

You could use D0 & D1 (Hardware serial) but then you lose your serial connection for debugging. However, it also uses D9 for power control which conflicts with the list of pins used by the lcd.

Sorry, what I meant was that if the comms on the GPRS Shield are D7&D8, does it have to be connected to D7&D8 on my Arduino Uno? You can't just change the programming?

Can I not run a wire from D7&D8 to lets say D2&D3 and tell my Uno to listen to D2&D3 on my the Uno digital inputs?

I originally thought the pins only had to be different because of stacking

You can run a couple of wires from the middle two pins of the Rx/Tx selection block to any two pins you like. But the fact that D9 is the software power switch may be a bit more difficult to overcome?

dannable:
You can run a couple of wires from the middle two pins of the Rx/Tx selection block to any two pins you like. But the fact that D9 is the software power switch may be a bit more difficult to overcome?

Couldn't I just move D9 as well?

Would this give me any problems?

P.S. The Uno board and rest of the stuff should be coming in this Monday. Purchased AT&T Go Sim yesterday. Searched the forums and people confirmed it working with GPRS shield in USA, might need to call for activation or something. Saw a few people had trouble with it at first.

Moving D9 will involve cutting tracks on the pcb. If you are happy with that then it should be ok. Personally I would avoid D13 with it having the on board led connected to it.

dannable:
Moving D9 will involve cutting tracks on the pcb. If you are happy with that then it should be ok. Personally I would avoid D13 with it having the on board led connected to it.

You mean cut the headers attached to the pcd? If so then I am okay with that. I can unsolder the 2 sided header, cut a pin out and replace it with a 1 sided pin.

By the way, thanks for all the help dannable, I really appreciate it. Hopefully everything goes smooth tomorrow when I get the package. If this whole thing goes smooth I'll see if I can make a "How To" for the forum.

Just an update.

Found a solution to the moving of pins without damaging any of the boards. Well I did have to unsolder and solder some double sided headers on Uno.

You can use a Protoshield to re-route some of the pins and just stick it to the back of the GPRS shield. Luckily I bought the Uno starter kit that came with the proto.

(P.S. Had to learn about solder iron tip care the hard way... )

Heres a video of how high it stacks lol.

Yes, it will work fine if everything installed properly and all combination are updated..