Can a phone turn a lock servo or stepper motor?

[bruceb]

Hi everyone,

I am looking for a regular GSM phone (like a Nokia) to turn a servo or stepper motor when a signal is received. Can I bank on the Lithium battery of the phone for tihs purpose when the servo is turned ON only few times a day? Would it be possible to connect the servo directly to the phone battery diodes while phone is in operation?

I'd rather use a GSM phone than to resort to some controller board like Arduino + a GSM module + ....
My main problem is power as I have to use AA batteries or Lithium ion batteries.

Thanks

 

[nandhu015]

I think it is not possible without a controller like Arduino. But you can replace GSM module with Nokia or any other phones(not all the models, only few models can be connected to controller).

 

[bruceb]

I think it is not possible without a controller like Arduino. But you can replace GSM module with Nokia or any other phones(not all the models, only few models can be connected to controller).

If I involved something like Arduino then I can't run the motor using AA batteries or Lithium ion batteries and my project would fail because I can't provide it cabled power from the socket.

What about the vibrator inside the phone? I mean that is a motor and it works.

Thanks

 

[bobstay]

I think what you are trying to do is possible. A few points:

• You will almost certainly need a microcontroller of some sort, especially if you want to use an RC servo which needs a PWM (Pulse Width Modulation) signal.
• Most phones run off a single cell lithium-ion battery. These provide between 3.3V (empty) and 4.2V (charged). Most microcontrollers (PIC/AVR) will run directly from these voltages.
• Most RC servos want voltages around 5-6V. You might find that they work with lower voltages - experimentation will be needed here.
• Whether or not you can run from the phone's internal battery or not depends largely on whether you're willing to open up the phone. If you don't mind hacking it around, you'll be able to connect to its internal battery and data lines. You also need to think about how long the battery needs to last in your application.
• You might be able to get away with using the vibrator motor directly. If you're willing to open and destroy the phone, and this motor is powerful enough for your needs, then you can set the phone to vibrate, and incoming calls/texts will trigger the motor. Then you could get away without using a microcontroller. Bear in mind this method is prone to false positives (marketing calls/texts, wrong numbers, vibration for other reasons (e.g. low battery))
• If you do use a microcontroller, like an arduino, you'll need to interface it to the phone somehow. Most modern phones have a USB port, but this is usually a "device" USB port, designed to be a slave to a computer, not a "host" USB port which will be what the microcontroller generally expects to be connected to. One alternative to get around this is to use an older phone which has RS232 serial lines on its connector, which will interface more-or-less directly to an arduino's serial port. You'd have to do some research to find a phone which has this.

 

[bruceb]

Bobstay - Thanks a lot for the feedback. I am willing to open the phone (something like a Nokia 1100)

1- So, this won't be as easy as replacing the vibrator with a servo?
2- Do I need Arduino or can I get away with an MCU to control the motor?
3- How would an MCU connect to a phone? phone to serial and serial to MCU?
4- I can power MCU and Motor using a 9V battery or other type of batteries as that won't be ON all the time so it should last for long time. Am I right with that assumption?
5- It would be great to read content of an SMS - I guess that's where the MCU come into play?
6- If I were to play with MCUs and I am very new to all this but I have programming experience (C, Bash, PHP....) then what kit or what type of MCU do you recommend me to go with?

Thanks a lot,

 

[nandhu015]

2- Do I need Arduino or can I get away with an MCU to control the motor?

You can use any microcontroller, but it seems you are new to microcontrollers, i would suggest you Arduino.

I can power MCU and Motor using a 9V battery or other type of batteries as that won't be ON all the time so it should last for long time. Am I right with that assumption?

Microcontroller has be working all the time, but it wont consume a lot of power.

It would be great to read content of an SMS - I guess that's where the MCU come into play?

Yes, But it also controls the pulse width to drive the motor.

 

[bruceb]

Thanks nandhu015.

So, I gather I need the following:
Arduino UNO or Arduino NANO?!
Servo
Phone
Battery

Is that all I need?

Thanks

 

[bobstay]

I would suggest that your first step, before buying any microcontrollers or other hardware, would be to get hold of whatever phone you're going to use, and try to connect to it using your computer.

For this you'll need a cable of some sort, or to solder to whatever internal contacts the phone has. A quick google shows that for a Nokia 1100, the data port pinout is like this: . So I would recommend getting hold of, or making, the required cables, and getting a usb-to-serial converter, and try getting it working with your PC. When you've done that, and can successfully communicate with it, then it's time to start thinking about microcontrollers.

To answer your question 1 about replacing the vibrator with a servo... short answer, no, it's not that simple. A servo is a motor, plus a gearbox, a variable resistor connected mechanically to the motor, and a little circuit which takes a PWM signal and moves the motor to the desired position by comparing the PWM signal to the position of the variable resistor. The vibrator, especially in older phones, is just a motor with an aysmmetric weight on its shaft. (newer phones use a vibrating weight on a spring). You could rip out the circuit board from the servo, and connect the servo's motor in place of the phone's vibrator motor. The problems with doing that are:

• The servo's motor may need a higher voltage than the phone provides
• The servo's motor may draw more current than the phone is expecting, which might damage the motor driver circuitry in the phone
• The motor will only turn in one direction, which probably isn't what you want.

So if you want to be able to (for example) rotate a camera or something with this project, just replacing the vibrator motor with a motor from a servo probably won't do what you want.

Can you tell us what it is that you want to make?

Edit: To answer some of your other questions:

2- Do I need Arduino or can I get away with an MCU to control the motor?

6- If I were to play with MCUs and I am very new to all this but I have programming experience (C, Bash, PHP....) then what kit or what type of MCU do you recommend me to go with?

Well, an Arduino is a microcontroller. I haven't used an arduino myself, but I have used AVRs, and an arduino is just an AVR with a bit of extra user-friendly software on top. A lot of people find Arduinos an easy route into using microcontrollers, so they might be your best bet.

3- How would an MCU connect to a phone? phone to serial and serial to MCU?

Yes, that's the general idea, but as I mentioned above, the phone you are suggesting doesn't seem to support serial directly - it uses something called F-Bus, which will require you to do a little more research into the protocol. It does seem that people have used F-Bus with microcontrollers, though. A word of warning about serial ports, too - PC serial ports use +/- 12V for their signals, which is generally too great a voltage for phones and MCUs to deal with. Phones and MCUs tend to use 0-3V or 0-5V (with the same protocol) so you will probably find you need a level-shifter IC like a MAX232 to get your MCU and/or phone to talk to a PC. When you get the MCU talking directly to the phone, you will probably be able to dispense with the level shifter.

4- I can power MCU and Motor using a 9V battery or other type of batteries as that won't be ON all the time so it should last for long time. Am I right with that assumption?

You can do this, yes - but you will need a voltage regulator to drop the 9V from the battery to 5V or 3.3V for the MCU. An alternative might be three AAs, which would give you 3.6-4.5V (depending on whether you use rechargeables or alkaline) - which could run the MCU directly. As nandhu015 mentions, the microcontroller will need to be on all the time, but if you're careful about putting it into sleep mode, most of them can power down so they consume only a few microamps.

5- It would be great to read content of an SMS - I guess that's where the MCU come into play?

Yes, you'll definitely need an MCU for that.

 

[bruceb]

bobstay - You have opened my eyes to new things. Thank you over and over.

I am not stuck with Nokia 1100; In fact, I don't have one yet. So, if you have a recommandition for a cheap phone that is simpler I can appreciate it. I also checked the option of GSM Shield for Arduino but staying away from that because of costs and power consumption as I am assuming a shield consumes much more power than a cell phone running on it's own battery.

Why are there shields (I take it shields are add-on modules for Arduino) for motors? what is the need for it when motor can directly connect to shield?

I picked the Nokia 1100 because of long standby time but I am not limited to that and open to suggestions.

 

[asleydyasley]

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