ActivityBot circuit "Check Pushbuttons"

PhilipWong

Hi everyone,

I'm new to electronic, micro-controller and robotic. I've brought an activitybot kit and are following the tutorials online to learn the basics. I'm up to the Check Pushbuttons tutorial, in it it says if we don't have a 100 ohm resistor we could use a 220 ohm instead. So I'm wondering what is the difference if I use a 100 ohm resistor or a 220 ohm resistor? Also what are the purpose (i.e. what does it do and how does it effect the performance of the circuit) of the 100 ohm reiestor?

Secondly I'm wondering if I use let say 220ohm (or other resistors) instead of the 10k ohm resistor, how will it affects the active high function in the circuit

thanks,
Philip

Jessica Uelmen

Hi Philip,

First, welcome to the wonderful world of electronics and to the forums!

By definition, a resistor resists the flow of electrical current. The higher the value, the greater the resistance.

In your example, the resistor is used to protect the I/O pins from accidental damage. This could happen if you set the pin as an input, but then accidentally write code to output a voltage to the pin. In these cases, the resistor prevents the pin from blowing out. Because of this, substituting a slightly higher value of 220 ohms doesn't effect the performance of the circuit.

In the case of the 10k resistor, it's acting as a pull-down resistor and his holding the voltage at 0 V when the button is not pressed. When the button is pressed and 5V is introduced into the circuit, the 10k resistor also prevents an electrical short.

I hope this helps, and let us know if you have any other questions!

Cheers,
Jessica

PhilipWong

Jessica Uelmen wrote: »

Hi Philip,

First, welcome to the wonderful world of electronics and to the forums!

By definition, a resistor resists the flow of electrical current. The higher the value, the greater the resistance.

In your example, the resistor is used to protect the I/O pins from accidental damage. This could happen if you set the pin as an input, but then accidentally write code to output a voltage to the pin. In these cases, the resistor prevents the pin from blowing out. Because of this, substituting a slightly higher value of 220 ohms doesn't effect the performance of the circuit.

In the case of the 10k resistor, it's acting as a pull-down resistor and his holding the voltage at 0 V when the button is not pressed. When the button is pressed and 5V is introduced into the circuit, the 10k resistor also prevents an electrical short.

I hope this helps, and let us know if you have any other questions!

Cheers,
Jessica

Hi Jessica,

Aha, I see now. Thank you.

Philip