INFO: Powering Devices With Chronos [29142]

This article applies to:
Chronos

 
Detail
Warning: Improper use of Chronos may void your warranty.

Chronos has both Digital Outputs and Analog Outputs available which can be used to control motors. Chronos can control motor devices with millisecond precision.

NOTE: Motors may take some time to power up (i.e., latency of the motor itself).

The Digital Outputs are essentially on/off (i.e. 0v and 5v).

The Analog Outputs are a range of voltages (i.e. 0v to 3.3V).

The Pulse Generator is a Digital Signal (on/off - 0v/+5v).

Chronos guarantees that it can provide 100mA. In general, it is found that Chronos can supply around 150mA. The maximum amperage that can occur from a single Digital Output is 20mA. An external power source may be required if more than 100mA is required.

At a minimum, flyback diodes should be used to protect Chronos when powering a motor. Damage caused by failure to use appropriate circuit protection (e.g. flyback diodes on inductive loads like motors) is not covered by the warranty.

These diodes should be in the reverse bias condition during normal operation (i.e. triangle facing the output instead of ground). When the power is cut to the motor, the energy stored in the motor's rotational inertia feeds power back into the circuit in reverse; the diode provides a safe path for that current to flow. Otherwise, Chronos could experience voltages in the negative hundreds.

While more difficult, we recommend wiring up an external power supply with a 3V regulator (e.g., with it's associated design requirements, bypass capacitors, heat dissipation) and some transistors to switch the motors on and off. We encourage the use of MOSFETs because they are easier to design with than BJT (no resistors). For example, this is an N-FET between the motor GND pin and the actual GND pin (i.e. low-side switch). Low-side switches have normal logic (i.e., 'high' voltage to gate = conducting state). Possibly adding a resistor on the power rail to the motor can make the short-circuit current stay at a safe level. Connect to Chronos digital outputs via aux cable or I/O Expander. This is the optimal and safest solution which provides full power to the motors.

Another solution can use Chronos' 5V power on the aux cable or I/O Expander instead of an external power supply. For example, the motor in the link appears to max out around 3.6V (https://www.precisionmicrodrives.com/product/307-103-9mm-vibration-motor-25mm-type). Therefore, a regulator and transistor are still needed.

The last solution could use the Chronos DAC (Digital Analog Channel) outputs. According to the performance sheet, setting a Chronos DAC output to 0.24 (e.g. 0.8V) lines up with the maximum current of a given DAC output (about 20 mA) and should provide perceptible vibration (the link suggests about 0.75g or 1/10th max amplitude). The advantage here is simplicity - no regulator, no transistors, no resistors. However, the flyback diode is still needed.

Running one motor is about the limit for Chronos. More motors can be run by they will be weak.
 
If you have any questions or concerns about your configuration, please contact Product Service & Support.

See Also:
INFO: Chronos Warning: Driving Induction Load [25077]
INFO: Connecting third-party switches to Chronos [30394]