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Postby dariosm » Fri Sep 22, 2017 7:40 pm

Hi you all, I'm wondering if this is the right forum to place this kind of question. I'm loving ModMyPi website and the product options available.
I'm preparing an IoT Introductory class, based on sensors mostly, initially for high school students. I've a very low budget to work with, but I want to give the students a complete kit to practice with, and start their own projects, wichi I'll be supervising later on.
So, I wonder if you guys can point me in the right direction on choosing the right kit for the students, preferently the ones that requires no soldering or electronics skills.
Thanks in advance.
Dario

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Postby Dave » Mon Sep 25, 2017 11:02 am

Hi Dario,

You have a couple of options:

YouTube Workshop Kit

For a real budget solution we have our YouTube workshop kits - https://www.modmypi.com/raspberry-pi/se ... rkshop-kit

This comes with a few sensors (PIR a.k.a Motion, Light, Temperature) as well as other interactive components like a buzzer, buttons and LEDs. It also has a step by step guide available as a PDF file or YouTube video. This is a great kit for beginners and people looking to get their foot in the door with electronics/programming. No soldering is required as it all plugs into the supplied breadboard using jumper wires. You then wire the breadboard up to the GPIO of the Raspberry Pi using jumper wires too.

Dexter GrovePi

The other option, which has a higher price point, is to look into the Dexter GrovePi solution. We offer various kits - https://www.modmypi.com/raspberry-pi/se ... oards-1062 - as well as individual sensors specifically designed for the GrovePi infrastructure - https://www.modmypi.com/electronics/grove/grove-sensors.

As with the YouTube workshop kit, no soldering is required, but instead of using a breadboard, the sensors all connect to a main controller board via the Grove sockets. The main control board then attaches directly to the Raspberry Pi.

I should also mention our Budget Kits containing the bare minimum to get you up and running with the Raspberry Pi in the first place - https://www.modmypi.com/search/?search=budget%20kit. You'll just need to source your own keyboard/mouse as well as a TV/monitor. We do have a budget keyboard/mouse combo here - https://www.modmypi.com/raspberry-pi/ac ... h=MMP-0242

If you have any more questions feel free to fire away!

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Postby BMS Doug » Tue Sep 26, 2017 8:57 am

Pi Selection:

The ideal pi for IoT is the Pi zero wireless but it isn't the best Pi for learning on (Pi3 is much easier to connect initially). Fortunately you can now buy them with a pre-Soldered header.

The biggest disadvantages of the Pi Zero can be fairly easily offset, a 3 port USB Hub with ethernet is available as a purchase option for any Pi Zero (£7.20 extra), mini HDMI to HDMI adapters are similarly offered as an option (from £1.50 to £6.60 extra depending on item).
No costs have been included below for micro SD card, power supply or case.

Pi0W:
Pro:
Cheap (£9.60 each for the pi, does not include any essential equipment such as micro SD card, power supply or case)
Wifi
small form factor

Con:
only 1 USB port (micro).
miniHDMI connection
GPIO Header not soldered on
Only available to buy 1 at a time.

Pi0W-Header
Pro
Wifi,
still pretty cheap (£13.99 each for the pi, does not include any essential equipment such as micro SD card, power supply or case)
Multi-order upto 20 at once
small form factor

Con:
only 1 USB port (micro).
miniHDMI connection


Pi3B
Pro
Wifi,
Ethernet
4 standard USB ports
standard HDMI connection
No order quantity limits

Con:
most expensive Pi (£31.99 each for the pi, does not include any essential equipment such as micro SD card, power supply or case)
Larger Form factor.

Pi1B+
Pro
Ethernet
4 standard USB ports
standard HDMI connection
No order quantity limits

Con:
No Wifi
cost (£25.99 each for the pi, does not include any essential equipment such as micro SD card, power supply or case)
Larger Form factor.

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Postby dariosm » Fri Sep 29, 2017 12:51 am

Thank you both for your great answers. They are very helpful.
I think my best option is the Raspberry Pi Zero.

I should have mentioned, though, that I don't mind soldering the header to the board. I just want to keep students off electronic components and soldering tasks, thus a plug'n'play-like solution would be nice.
That's why I like a lot the grovepi shield/board and the sensors available for it, since they have the plug and play feature I mentioned (every sensor is on its pcb with the required circuit to make it work out of the box, and of course, its connector).

Sadly, I've found that this kind of sensors are expensive: some of they are as expensive as the complete 34 sensors kit. I'm wondering if it is possible to use this kit, with some additional adapters to avoid the expensive groovepi and its customized sensors.

Thanks again!

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Postby BMS Doug » Fri Sep 29, 2017 9:39 am

dariosm wrote:Thank you both for your great answers. They are very helpful.
I think my best option is the Raspberry Pi Zero.

I should have mentioned, though, that I don't mind soldering the header to the board. I just want to keep students off electronic components and soldering tasks, thus a plug'n'play-like solution would be nice.
That's why I like a lot the grovepi shield/board and the sensors available for it, since they have the plug and play feature I mentioned (every sensor is on its pcb with the required circuit to make it work out of the box, and of course, its connector).

Sadly, I've found that this kind of sensors are expensive: some of they are as expensive as the complete 34 sensors kit. I'm wondering if it is possible to use this kit, with some additional adapters to avoid the expensive groovepi and its customized sensors.

Thanks again!


I didn't mention the Pi Zero as it isn't really suitable for IoT use (no WiFi, no built in ethernet) The Pi Zero W is a better choice.
The base models of Pi Zero (and Pi Zero W) are only available to be purchased 1 per order, the version with the pre-soldered header increases the order quantity limit to 20.

In my opinion you might be best served with a collection of mini solderless breadboards available in a range of different colours.

You can then pre-configure the mini breadboard for each sensor so that your students don't have to do the electronics themselves.

I will mention (Warning, blatant plug) the PUD board which allows safe and easy connection of up to 6 digital inputs (such as switches, buttons, rotary encoders, etc.). This board gives a 10k resistor user configured to Pull Up or Pull Down the input (results less reliable if left floating) and a 1k current limiting resistor to protect the GPIO pin from inadvertent short circuits.


If you were to get the 34 piece sensor kit you would also need some breadboard (usually done with one large breadboard but as I said above, preconfiguring some smaller breadboards might be better for you), Jumper wires (mostly male to female, some male to male), At least one ADC chip (Analogue to digital converter) and a selection of resistors and transistors.

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Postby dariosm » Fri Sep 29, 2017 7:21 pm

BMS Doug wrote:
dariosm wrote:Thank you both for your great answers. They are very helpful.
I think my best option is the Raspberry Pi Zero.

I should have mentioned, though, that I don't mind soldering the header to the board. I just want to keep students off electronic components and soldering tasks, thus a plug'n'play-like solution would be nice.
That's why I like a lot the grovepi shield/board and the sensors available for it, since they have the plug and play feature I mentioned (every sensor is on its pcb with the required circuit to make it work out of the box, and of course, its connector).

Sadly, I've found that this kind of sensors are expensive: some of they are as expensive as the complete 34 sensors kit. I'm wondering if it is possible to use this kit, with some additional adapters to avoid the expensive groovepi and its customized sensors.

Thanks again!


I didn't mention the Pi Zero as it isn't really suitable for IoT use (no WiFi, no built in ethernet) The Pi Zero W is a better choice.
The base models of Pi Zero (and Pi Zero W) are only available to be purchased 1 per order, the version with the pre-soldered header increases the order quantity limit to 20.

In my opinion you might be best served with a collection of mini solderless breadboards available in a range of different colours.

You can then pre-configure the mini breadboard for each sensor so that your students don't have to do the electronics themselves.

I will mention (Warning, blatant plug) the PUD board which allows safe and easy connection of up to 6 digital inputs (such as switches, buttons, rotary encoders, etc.). This board gives a 10k resistor user configured to Pull Up or Pull Down the input (results less reliable if left floating) and a 1k current limiting resistor to protect the GPIO pin from inadvertent short circuits.


If you were to get the 34 piece sensor kit you would also need some breadboard (usually done with one large breadboard but as I said above, preconfiguring some smaller breadboards might be better for you), Jumper wires (mostly male to female, some male to male), At least one ADC chip (Analogue to digital converter) and a selection of resistors and transistors.



Sorry, meant to say Pi Zero W! Of course, connectivity onboard is required for IoT.
I appreciate your suggestion regarding coloured mini breadboards to pre-install or the circuit requirements for each sensor to work. But 34-sensor kit, though, seems to include already pre assembled sensor and circuit units (pull-down/up resistors, capacitors, and whatever needed in each case), so as far as I understand, in most cases just the sensor pcb from the kit and the Pi board (plus wires) should be enough. Right?

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Postby BMS Doug » Tue Oct 03, 2017 9:47 am

As I understand it the Kit was originally designed for arduino rather than Pi but can be used with the Pi with a few additional components.

Here's a breakdown of parts:

Joystick
An analog 2-axis joystick with 2x 10K ohm pots and push button function.
Connector pin descriptions are printed on the PCB. A push-on operating
knob is included with the module.
this needs an Analogue to Digital Converter (ADC) before the Pi can make any sense out of it.

Relay
A relay module suitable for direct connection to an Arduino board. The
module requires 5 V power supply. The input control signal is identified with
an ‘S’. The relay has one change-over contact. It is capable of switching
resistive loads up to 10 A at 250 VAC and up to 10 A at 30 V maximum.
Don’t forget to provide interference suppression for the switched load!

May require a transistor to provide the switching voltage as the Pi GPIO are only 3v3 not 5v. It does look like the module has 3 pins so it is possible that there is an onboard transistor.

Big Sound
A microphone module featuring a high-sensitivity large-format electret
capsule. Output ‘DO’ (active high) is switched when the sound level
exceeds a preset level. A pot allows adjustment of the level. The analog
output signal is available at the ‘AO’ pin.

Digital output could be directly connected to the pi, analogue output will require an ADC.

Small Sound
A microphone module with a small electret capsule. Output ‘DO’ (active
high) is switched when the sound level exceeds a preset level. A pot allows
adjustment of the level. The analog output signal is available at the ‘AO’
pin. Except for the smaller size of the capsule and its lower sensitivity the
module is identical to the ‘Big Sound’ module.

Digital output could be directly connected to the pi, analogue output will require an ADC.

Tracking
IR light reflection switch, useful for obstacle avoidance or line following
on models that move around the floor. An obstacle in front of the
sender/receiver diodes will cause the ‘out’ pin to be pulled low (active
low). A pot allows adjustment of the circuit’s sensitivity. The detection
distance can be up to approximately 1 cm.

Digital output, this can be directly connected to the pi.

Avoid
IR-reflection sensor, useful for obstacle avoidance applications. When
an obstacle is in front of the IR sender/receiver the ‘Out’ pin is switched
low (active low). The circuit sensitivity can be adjusted with a pot. The
obstacle detection distance can be adjusted up to approximately 7cm.
An enable (EN) jumper can be fitted for continuous operation. Removal
of the EN jumper allows an external logic signal (at the EN pin) to switch
the detector on and off (low = active, high = off).

Digital output, this can be directly connected to the pi.

Flame
A sensor module to detect flames. The spectral sensitivity of the sensor
is optimized to detect emissions from naked flames. The output signal
‘DO’ is pulled high (active high) when a flame is detected. The switching
threshold is adjustable via a preset pot. An analog output signal from
the sensor is available at pin ‘AO’.
 Typical spectral sensitivity: 720-1100nm
 Typical detection angle: 60°

Digital output could be directly connected to the pi, analogue output will require an ADC.

Linear Hall Sensor
Linear Hall Sensor module to detect the presence of a magnetic field near
the sensor. Variables such as field strength, polarity and position of the
magnet relative to the sensor will affect point at which the ‘DO’ output
switches to a high level (i.e. active high). The circuit sensitivity can be
adjusted with a pot. An analog output signal from the sensor is available
at pin ‘AO’.

Digital output could be directly connected to the pi, analogue output will require an ADC.

Touch
Touch sensitive switch. Touching the sensor pin produces an output at the
‘DO’ pin. The output is not a clean signal but includes 50 Hz mains induced
signals (‘mains hum’). The output signal is ‘active high’ and the circuit
sensitivity can be adjusted with a pot. An analog output signal from the
sensor is available at pin ‘AO’.

Digital output could be directly connected to the pi, analogue output will require an ADC.


Digital Temp
Temperature sensing module using an NTC thermistor. The output signal
at ‘DO’ switches high when the preset (adjustable) temperature is
reached. An analog output signal from the sensor is available at pin ‘AO’

Digital output could be directly connected to the pi, analogue output will require an ADC.

Buzzer
Electronic buzzer for 5 V operation. Ensure correct polarity!!
Positive supply to the ‘-’ pin and ground to the ‘S’ pin!
Data: Typical operating frequency 4000Hz at 80dB min, 5V DC at 5mA typical
TMB12A05 or equivalent.
Tip to avoid mix up: The buzzer housing is slightly taller than the loudspeaker
housing and has a label showing the + pin ident.

May require a transistor to provide the switching voltage as the Pi GPIO are only 3v3 not 5v. It does look like the module has 3 pins so it is possible that there is an onboard transistor.

Passive Buzzer
Mini loudspeaker module ca. 16 Ohm Impedance, (maximum continuous current
through the speaker coil is approximately 25 mA.) Don’t mix this one up with the
buzzer module! The outer two pins connect to the speaker. Polarity is unimportant.
Tip to avoid mix up: The loudspeaker housing is not as tall as the buzzer housing.

I'm fairly sure this will need additional circuitry.

RGB LED
RGB-LED with clear lens and built-in 150 ohm series resistor for 5 V operation. The
PCB printing is incorrect, it shows the blue and red connections switched. The LED
has a common cathode (the ‘-‘ Pin).

Requires a transistor for the Pi to provide the required 5V supply.

SMD RGB
RGB-LED with an SMD housing and no series resistor. The PCB printing is incorrect, it
shows the green and red connections switched. The LED has a common cathode (the
‘-‘ pin). A suitable resistor value would be 220 ohms.

Requires resistors to limit the current through the LEDs.

Two-Color 5mm
The 5mm LED has a common cathode connected to the ‘-‘ pin on the PCB. The
centre pin connects to the red anode and the ‘S’ pin connects to the green
anode. No series resistor is included in the circuit. A suitable value for low
voltage operation would be 220 ohms.

Requires resistors to limit the current through the LEDs.

Two Color 3mm
The 3mm bi-color LED has a common cathode (- pin), connected with the ‘-’ pin on
the PCB. The centre pin activates the red light and the ‘S’ pin the green light. No
series resistor is included in the circuit. A suitable value for low voltage operation
would be 220 ohms.

Requires resistors to limit the current through the LEDs.

Reed Switch
This reed switch offers an analog as well as a digital interface. The ‘G’ pen is
connected to GND, the ‘+’ pen to 5V DC, the ‘AO’ pen offers the analog
output while the ‘DO’ offers the digital output. A potentiometer is used as a
pull up resistor.

Likely to have a 5V digital output so requires a voltage divider before being used on a Pi. Connecting supply voltage to 3v3 instead of 5V might work to bypass the requirement for a voltage divider.
Analogue output would require an ADC to interpret.

Mini Reed
The reed switch is connected between the two outer pins on the PCB. Without a
magnetic field the contacts remain open.
A built-in 10 K ohm resistor is connected between the centre pin and the ‘S’ pin.
It can be used as a pull up or pull down resistor.

Should work OK with the PI provided the module is supplied with 3v3 not 5v

Heartbeat
This module consists of an IR-LED and a photo transistor which can be used to read a
pulse when a fingertip is positioned between the LED and photo transistor.
The module requires additional external circuitry. A 330 ohm series resistor for the
LED is included. The 5 V supply connects to the centre pin, ground to the ‘-’ pin. The
photo transistor signal is available on the ‘S’ pin which has a built-in pullup resistor.


7 color flash
Clear 5mm LED for direct operation from 5V. The LED color automatically
cycles through a seven-color sequence. The 5 V supply connects to the ‘S’ pin
and ground on the centre pin.

May require a transistor to provide the switching voltage as the Pi GPIO are only 3v3 not 5v.

Laser emitter
Red Laser module for direct connection to a 5 V supply. Connect the 5 V supply to
the ‘S’ pin and ground to the ‘-’ pin. Transmission wavelength: 650nm

Not supplied as not believed to meet with UK regulations on laser modules

PCB mounted push Button
A built-in 10 K ohm resistor is connected between the centre pin and the ‘S’ pin and
can be used as a pull up or pull down resistor. The push button connects the two
outer pins.

Adding an in-line current limiting resistor is recommended as it eliminates the risk involved with accidentally shorting a GPIO set as an output. (programming error can damage your pi unless you take the precaution).
The PUD board is suitable for use with this module, either bypassing the modules built in PUD resistor or bypassing the PUD board resistor.

Shock, a rolling-ball type tilt switch.
A built-in 10 K ohm resistor is connected between the centre pin and the ‘S’ pin
and can be used as a pull up or pull down resistor. The switch contacts connect to
the two outer pins.

Adding an in-line current limiting resistor is recommended as it eliminates the risk involved with accidentally shorting a GPIO set as an output. (programming error can damage your pi unless you take the precaution).

Rotary encoder
Rotary encoder useful for making an electronic pot etc. Connection idents are
printed on the PCB.

Adding an in-line current limiting resistor is recommended as it eliminates the risk involved with accidentally shorting a GPIO set as an output. (programming error can damage your pi unless you take the precaution).
Adding a pull up or pull down resistor could improve signal quality.
The PUD board is suitable for use with this module.

2x Light Cup
This module incorporates a mercury tilt switch and clear red LED. ‘G’ is the
common connection to the LED cathode and one terminal of the switch. ‘S’
is the other switch contact and ‘L’ connects to the LED anode (a series
resister is required for the LED, 220 ohms for example). The ‘+’ pin
connects to a 10 K ohm pullup resistor connected to ‘S’ of the switch.

Not supplied due to mercury content.

Tilt Switch
Mercury tilt switch which makes or breaks depending on its attitude.
Rolling ball tilt switch
A built-in 10 K Ohm resistor connected between the middle and ‘S’ pin is available
for pull up or pull down use. The switch contacts connect to the two outer pins. Load
switching max: 12VDC 50mA

Not supplied due to mercury content.

Photoresistor
LDR (Light Dependant Resistor). Dark resistance >20M Ohm, light <80 Ohm. The
two outer pins connect to the LDR. A fixed 10 K ohm resistor connected between
the middle pin and the ‘S’ pin is included on the module. This simplifies the
building of a measurement bridge circuit.

external components required to change signal to a digital output or make it suitable for connection to an ADC.

Temp and Humidity
A module with a temperature/humidity sensor type DHT11, Temperature range :
0 - 50°C (+/-2°C), Rel. humidity: 20-95% (+/-5%), Supply voltage: 3 to 5.5V.
With a built-in 10 K ohm pullup resistor
.
can be connected directly to the Pi.

Analog Hall
The Hall-Sensor-Switch (bipolar) module features a 44E311, 3144EUA-S or
3144LUA-S sensor together with an LED and resistor. The LED switches on when a
magnetic field is detected. The ground pin is marked ‘-’, centre pin is +5 V supply
(Vs) and the output signal is on the ‘S’ pin.

Requires an ADC.

Hall Magnetic
A Hall sensor module with analog output signal. The ground pin is marked ‘-’,
centre pin is +5 V supply (Vs) and the output signal is on the ‘S’ pin.

Likely to have a 5V digital output so requires a voltage divider before being used on a Pi. Connecting supply voltage to 3v3 instead of 5V might work to bypass the requirement for a voltage divider, if so a current limiting resistor would be recommended.

Temp
A module with a digital ‘One Wire’ temperature sensor (DS18B20). A 4.7K ohm
pullup resistor is included for the bus signal. Additional sensors can be added to the
bus and individually addressed. Only one pullup resistor should be connected to the
bus, irrespective of the number of sensors connected.
 Temperature range: -55 to +125°C
 Typical accuracy: 0.5°C
 Resolution: 9-12Bit, depending on the program

requires a pullup resistor.

Analog Temp
NTC Temperature sensor module. The sensor resistance is approximately 10 k ohm
at room temperature. The NTC sensor is connected between the two outer pins. A
fixed 10 K ohm resistor connected between the middle pin and the ‘S’ pin is included
on the module. This simplifies the building of a measurement bridge circuit.
 Temperature range: -55°C to +125°C
 Accuracy: +/- 0.5°C

external components required to change signal to a digital output or make it suitable for connection to an ADC.

IR Emission
The IR-LED can be used to build a light barrier or an IR remote control signal
transmitter.

Might need a current limiting resistor.

IR Receiver
Infrared sensor type 1838 for use with 38KHz IR signals.
 Supply voltage: 2.7 to 5.5 V
 Frequency: 37.9 KHz
 Receiver range: 18m (typical)
 Receiving angle: 90°

Likely to have a 5V digital output so requires a voltage divider before being used on a Pi. Connecting supply voltage to 3v3 instead of 5V might work to bypass the requirement for a voltage divider, if so a current limiting resistor would be recommended.

Tap Module
Vibration sensor module. The momentary switch contacts are connected between the
two outer pins.

Adding an in-line current limiting resistor is recommended as it eliminates the risk involved with accidentally shorting a GPIO set as an output. (programming error can damage your pi unless you take the precaution).
Adding a pull up or pull down resistor could improve signal quality.
The PUD board is suitable for use with this module.

Light blocking
Slotted light barrier. The middle pin connects to + 5 V supply and the pin marked ‘-’
connects to ground. The output signal (with a 10 K ohm pullup to +5 V) is available on
the pin on the right.

Has a 5V digital output so requires a voltage divider before being used on a Pi. Connecting supply voltage to 3v3 instead of 5V might work to bypass the requirement for a voltage divider, if so a current limiting resistor would be recommended.

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Postby Dave » Tue Oct 03, 2017 11:29 am

Thanks BMS Doug for the very extensive post!

All the information there looks pretty on point.

Just a tiny thing to add:

Generally speaking, if a sensor requires 5v to operate, then its output is probably 5v as well. As Doug has already mentioned the Raspberry Pi's GPIO pins run off of 3v3 logic, so be sure to check how you are powering the sensor.

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Postby dariosm » Thu Oct 05, 2017 5:19 am

Thank BMS Doug! You were certainly clear and extensive enough to address every detail.
As you perfectly pointed out in each sensor case, the lack of ADC in Pi boards make impossible to directly connect some sensors. Arduino does it through its analog GPIO's.
And also a Pi board, like some other boards (esp based, for instance), does not work with 5v vcc, so that's another complication.

34-sensor kit seems more suitable for Arduino than Pi boards, so buying the kit together with a Pi might not be the right move if I want to work with them as-is. Experiments in the class would be very confusing, regarding I'm teaching to kids with zero knowledge in the topic.

Back to the board alternatives then. May be and Arduino Uno and the 34-sensor kit is the answer, adding some requirements to the class scenario: a PC and usb connection to the Arduino, both to upload code and to provide TCP/IP connectivity.
This would not be suitable as a stand alone prototype, but for the sake of simplicity it could be enough.

I couldn't find in the site any sensor kit that works directly with Pi boards (but Groove ecosystem). Cost is an issue here.

Anyway, may be Arduino gives me the balance I need taking into account cost and simplicity of usage.

Thanks all you guys for the help provided.

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Postby BMS Doug » Thu Oct 05, 2017 8:39 am

Arduino have Wifi or Ethernet modules available to convert your project to stand alone.


A pre-configured breadboard should be able to handle the necessary adaptions, the circuits are pretty simple and the components fairly cheap. there aren't a lot of different configurations needed.


The Raspio Analogue Zero will sit on top of a Pi Zero and give you 8 channels of analogue inputs.

The MyPiFi GPIO expander board gives you 16 channels of I/O which could be 5V tolerant (Dave can you confirm?)

Both of the above boards can be made up on solderless breadboards with very cheap components and easily googled instructions.
8 channel 5v tolerant I/O - MCP2308 £0.84ea (cheaper in multiples)

ADC chips vary in price depending on number of channels and resolution (number of bits) you only need 2 channels at most for any single sensor, An 8 bit ADC will convert the analogue signal into one of 256 discreet digital values, 10 bit gives 1028 discreet values. Arduino use 10 bit ADC but as low as 8 bit should be sufficient for demonstration purposes.
The MCP3002 is 2 channel 10 bit ADC £1.46ea (cheaper in multiples)

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