Can anyone please help me figure out a best way to connect many sensors to arduino micro using as less pins as possible? For my project I will be using about 10 sensors which include pressure, temperature and accelerometers. The output is through servos and it has to be 5V parallel digital.
Your help is much appreciated.
Thanks
I will be using 7 force sensors which look like in the image attached. These sensors will be attached to finger tips on a robotic hand that I am making. Also I will be using one 3 axis accelerometer placed in the palm of hand along with 2 small temperature sensors at joints of the fingers.
Any help on connecting these would be much appreciated. The actuators are 3 servos.
Also with this in mind, would you recommend arduino micro or nano? Because space is limiting factor for my hand project as it is designed for a child.
Thanks in advance.
Fruit123:
I will be using 7 force sensors which look like in the image attached. These sensors will be attached to finger tips on a robotic hand that I am making. Also I will be using one 3 axis accelerometer placed in the palm of hand along with 2 small temperature sensors at joints of the fingers.
Many of the Arduinos have six analog inputs.
You have a few options since your plan requires more than 6 analog inputs. Figure out a way to only use 6 analog inputs instead of the planned 7 analog devices. Use an analog multiplexer. Use an external ADC chip such as the MCP3208 (which has 8 analog inputs). I think I'd go with the external ADC chip myself.
I think the Pro Mini is one of the smallest Arduino boards (at least it's the smallest I've used). You'll need a USB to serial device to program the Pro Mini but these devices only cost a couple of dollars (as do Pro Mini clones).
The way you connect the other sensors depends on the exact sensor used. Many sensors can communicate with I2C but there are a bunch of other possible communication protocols they may use.
as DuaneDegn pointed out 'many' of the arduino, but really the UNO and then, the UNO with the DIP chip. or any UNO that with the SMT chip that does not bring the 2 extra pins out for use.
the NANO and MINI's all have the entire 8 analog pins of the SMT chip available.
to skirt the main, the TEENSY offers both higher resolution and more analog pins
I would offer that you can use a multiplexor that would act like an A or B switch so that two inputs can alternately be looked at by one analog pin.
however, as soon as you have to start looking at alternate chips, the possibility of using a single analog chip that has higher resolution and more features becomes more of an option.
this one has some support from the playground
http://playground.arduino.cc/Code/MCP3208
Thanks a lot for you help guys. Is there a way that I could connect the sensors with better efficiency of current? since connecting more sensors to the 5V on arduino would draw less current for each. Also would that not affect resistance of the sensors?
You could have a Darlington IC to turn on and off each sensor as required.
PS. The arduino's tend to only be able to pull 200mA MAXIMUM from the 5V pin before the regulator burns and dies a death.
Use say a 1A 5V adapter to power the arduino and then the sensors in parallel.
PS. No specs included for those sensors, so can not say if 1A is enough...but yeah.
PS. The arduino's tend to only be able to pull 200mA MAXIMUM from the 5V pin before the regulator burns and dies a death.
Very mixed up thinking there. You are conflating some facts and coming up with nonsense.
Exceeding 200mA has no effect on the regulator which can manage at least 600mA.
The 200mA is per 5V power pin of which there are two, so any limit is 400mA.
Grumpy_Mike:
Very mixed up thinking there. You are conflating some facts and coming up with nonsense.Exceeding 200mA has no effect on the regulator which can manage at least 600mA.
The 200mA is per 5V power pin of which there are two, so any limit is 400mA.
Ah my bad. So why can you only draw 200mA per pin? Someone somewhere just had written "only 200mA otherwise you burn out the reg" and I stuck with it since.
Ooops.
Seems if you want something done, do it yourself...or wait for Grumpy to correct you seems to be the best option :P.
So why can you only draw 200mA per pin?
No you can't. In the data sheet for the Atmega processors there is a list of absolute ratings, section 28. It says:-
DC Current per I/O Pin .................40.0 mA
DC Current VCC and GND Pins...... 200.0 mA
On an DIL package there are two Vcc pins and two Gnd pins. These are split into analogue and digital supply and ground but are connected together inside the chip. Therefore any current will be split in two, so the total draw from the supply can be 400mA as can the total current sink.
I suspect this limit is caused by the bonding wires into the chip. Where as the limit on the pins themselves is determined by the output FETs inside the chip.
There is also a bunch of other restrictions as to the total current distribution within pins.
“Max” means the highest value where the pin is guaranteed to be read as low
“Min” means the lowest value where the pin is guaranteed to be read as highAlthough each I/O port can sink more than the test conditions (20 mA at VCC = 5V, 10 mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed:
ATmega48PA/88PA/168PA/328P:
1] The sum of all IOL, for ports C0 - C5, ADC7, ADC6 should not exceed 100 mA.
2] The sum of all IOL, for ports B0 - B5, D5 - D7, XTAL1, XTAL2 should not exceed 100 mA.
3] The sum of all IOL, for ports D0 - D4, RESET should not exceed 100 mA.
If IOL exceeds the test condition, VOL may exceed the related specification. Pins are not guaranteed to sink current greater than the listed test condition.Although each I/O port can source more than the test conditions (20 mA at VCC = 5V, 10 mA at VCC = 3V) under steady state conditions (non-transient), the following must be observed:
ATmega48PA/88PA/168PA/328P:
1] The sum of all IOH, for ports C0 - C5, D0- D4, ADC7, RESET should not exceed 150 mA.
2] The sum of all IOH, for ports B0 - B5, D5 - D7, ADC6, XTAL1, XTAL2 should not exceed 150 mA.
If IIOH exceeds the test condition, VOH may exceed the related specification. Pins are not guaranteed to source current greater than the listed test condition.
This has nothing to do with the regulator which is on the board and is responsible for providing power to the chip. The rating on most Arduinos for this regulator is 1A but thermal considerations which depend on the input voltage limit any practical current to about 500 - 600 mA.
Someone somewhere just had written "only 200mA otherwise you burn out the reg"
There are a lot of simpletons out there.
Thanks guys
A quick question, what temperature sensor would you recommend if it was to be mountable on a finger of a robotic hand? it should cover 60 degreescelcius range and compatible with arduino board