HI,
I would like to know if I can connect to the 4 Analog Arduino pins to TSL251R-LF AMS-TAOS light sensors.
and four more Piezo electric actuators via the 4 digital output pins.
I would like to get your thoughts about the set up of the describe system in the power point sheet.
Thanks in advance
That is possible. The actuators MAY need extra electronics.
Their datasheets will show to interface them
I see that the light sensors are powered by 9V. What is the maximum output voltage of the sensors? If the max voltage is greater than 5V you can damage the input of the Arduino. Input voltage to any pin is maximum Vcc + 0.5V. You should have a resistor between the base of the transistor and the digital output to limit base current. 220 ohms or more. Is the transistor the right way around?
Hi,
Yes, indeed it seems that you are right, I have checked the schismatics in the light sensor datasheet.
It looks like the maximum Vdd voltage can go no higher than 5 V.
Furthermore, it is recommended to set a capacitor of 0.01 - 0.1 micro Farad in parallel to the sensor.
Thanks for that note!
I don't fully understand why I should place a resistor between the base of the transistor and the digital output pin - since I think that I can control the current using the sketch program (this is what I understood from the Arduino schematics).
Basically, I want to control the usage of the actuator, making it open or close when needed.
The maximum voltage allowed in the actuator is 24 V...
Regarding the alignment of the transistor, Yes you are correct again, I mixed the sides of the emitter and collector (my electronics knowledge is basic to say the least)...
Any additional advice will be fully appreciated 
transistor base resistor explains better than I can the requirement for the base resistor.
Look up voltage dividers. That is how to scale the output from the sensor to the less than 5 volts for the Arduino input.
Look into N-FETs to control your actuators. If properly chosen a N-FET will be more efficient than a bipolar transistor.
I think that I can control the current using the sketch program
I don't know how you would control current programmatically. The current is determined by the load resistance. If you are referring to PWM (analog output) you need to realize that PWM is not analog at all. The voltage from the pin is either 0V or 5V.
