hi,
i would like to connect the arduino to the following device:
that datasheet says that I should not exeed 3v in the data pin. If i connect this device directly to the arduino TX pin will be damaged?
how can I calculate the correct resistance if i don't know the mA that the device needs? I mean I found some calculators in internet:
but I'm not sure if it works for everything, and I don't know the mA that are needed.
sorry I'm a begginer with electronics. thx a lot
You've linked to a calculator for LED series current-limiting resistors - this isn't what you want.
Do you already have a separate 3V supply for the transmitter module?
no,
I was thinking to take the power from the arduino and place a resistor between. Like a LED. (?)
thx
It wont work the way you think it will, at the minimum what you need is a Voltage Divider
The easiest way would be to use a potentiometer, +5 on 1 side, ground on the other and output connected to the wiper in the middle
course this will change depending on the load you put on it and some other factors, another option would be to use a 3v regulator
The easiest way would be to use a potentiometer,
Yep that is the eases way to blow thing up.
that datasheet says that I should not exeed 3v in the data pin. If i connect this device directly to the arduino TX pin will be damaged?
So you need to cut down the signal from the arduino pin into this device. You can use a potential divider to do this but the best way is to use two transistors, as a simple two stage common collector amplifier. You need two stages because a single stage inverts the signal, so with two stages it is the right way up.
Hi thanks for the answers.
I understand now that with the voltage divider, i think i'm gonna use it. and also a 3v regulator for the whole circuit.
but i don't know what is a "simple two stage common collector amplifier". Does anybody have a link with the circuit? If this is better I would like to know how does it work.
thanks in advance.
but i don't know what is a "simple two stage common collector amplifier"
First diagram (Figure 1) on this page.
put a resistor (1K) in the base and wire it up to the TX of the arduino and wire the collector resistor to +3V3
Then use that circuit again and connect the base directly to the collector of the first transistor. Take the collector of the second transistor and connect that to the RX input of your device. Again wire the collector resistor to +3V3.
thank u so much
In the circuit, in the above link, where the resistor is added to the emitter side of the transistor, why isn't it possible to put the output on the emitter and use that as a non inverting output?
Martyn the electronics novice ;D