Every one of Marty's motors is a Smart Servo, that means it can provide feedback about its position, and the amount of electrical current going through the motor. In an electric motor, more current = more force, so this gives us a way to see how much force is on a joint!

===== In MartyBlocks =====

The motor current can be used as a sensor in MartyBlocks, look under the sensing blocks section:

{{ :martyv2:sensorsandaddons:scratch-acc-1.png?direct }}

Select a joint from the dropdown list in the Current block, and click the checkbox to display it.

Then, try asking Marty to move, and look at how the value changes.

==== Reacting to force ====

We can use the current input to get Marty to react when they sense a force. For example this code will raise Marty's arm, and then dance when you press it:

{{ :martyv2:sensorsandaddons:scratch-currentsense-1.png?direct }}

Note that we have to use a Hold block to get Marty to hold their joints in position - by default Marty is poseable when not moving - so will just let you move their arm.