I want to run a motor using an XBee module; depending on if the particular digital pin is 0 or 1 the motor is tuned off or on. These are tiny vibration motors that do not draw a lot of current. So, the easiset option is to connect them directly to the XBee digital out pin. However, I do not know the amount of current an XBee digital pin can source.
I am using XBee series 1 modules. Firmaware version 1084.
The product document mentions transmit current as 45mA at 3.3V and receive current as 50mA at 3.3V . My guess is that these are the values that that the module draws from its power source.
Can anyone point me to a document with the current ratings for the digital pins?
I want to run a motor using an XBee module; depending on if the particular digital pin is 0 or 1 the motor is tuned off or on. These are tiny vibration motors that do not draw a lot of current. So, the easiset option is to connect them directly to the XBee digital out pin. However, I do not know the amount of current an XBee digital pin can source.
I am using XBee series 1 modules. Firmaware version 1084.
The product document mentions transmit current as 45mA at 3.3V and receive current as 50mA at 3.3V . My guess is that these are the values that that the module draws from its power source.
Can anyone point me to a document with the current ratings for the digital pins?
regards,
A
At 45mA, you will definitely need a buffer/driver/relay.
The receive mode current is unrelated to the current sourcing or sinking capability of a digital I/O pin of the microprocessor - which is a member of the 8051 family.
Thanks Waltr and Stevech. Too bad I cannot use the series 1 models to directly power the motors.
My guess is that other models wont be able to source 45 mA either. Right now I am thinking of using a transistor switch to connect to the motors; the output from the XBee goes to the transistor and acts as the switch. The motors would be connected to the power source via the transistor.
Does that sound reasonable? Does anyone have a simpler ideas that lead to more compact solutions?
Yep, there are very few if any logic chips that can source/sink 45mA so the drive transistor is good design practice. An NPN transistor would work perfectly. Connect the emitter to ground, the collector to the motor. the other end of the motor the +V. Use a resistor of above 1k to 4.7k from the XBee output pin to the base.
Don’t forget a diode across the motor terminals to clamp the back-EMF.
There are a number of transistors in SOT-23 SMD packages that are rather small and can easily switch 45mA. The one I commonly use is the FMMT491.