User Manual

ManualsBrandsRobot Power ManualsBrushed DC Motor ControllersArduino Compatible Mega Motor Shield 13A, 5-28V

Version 1.5 - December 11, 2010

MegaMoto User Manual

Thank you for your purchase of the Robot Power MegaMoto™ motor control shield for

Arduino™. This manual explains the features and functions of the MegaMoto along with

some tips for successful application. Before using your MegaMoto you must read and agree

to the disclaimer printed at the end of this document. If you don’t agree please return your

unused MegaMoto to Robot Power for a refund.

The Robot Power MegaMoto is a low-cost easy to connect general-purpose power amplifier

designed to work with the Arduino hardware compatible CPU units. The MegaMoto can be

configured as a single H-bridge circuit or as two independent half-bridge circuits. While

designed for permanent magnet brushed DC motors; the MegaMoto is suitable for a wide

range of DC loads as long as they are within the current and voltage envelope of the device.

Figure 1. MegaMoto top view

Summary of content (13 pages)

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MegaMoto User Manual Thank you for your purchase of the Robot Power MegaMoto™ motor control shield for Arduino™. This manual explains the features and functions of the MegaMoto along with some tips for successful application. Before using your MegaMoto you must read and agree to the disclaimer printed at the end of this document. If you don’t agree please return your unused MegaMoto to Robot Power for a refund.
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1. Specifications Voltage Range Current (H1 bridge) Current (each halfbridge) Current (ganged half-bridge) PWM frequency Current Sense Output Input voltage levels Size Mounting 1. 6V – 24V (28V absolute max) 13A cont. at 100% duty cycle 12A cont. at 70% 30A - 5 second peak Same as above Double above DC – 20kHz Vc = I * 0.075 Vc = .0.75 at 10A Vc = 2.99V at 40A 2.5V – 5.5V = logic high <1.7V = logic low 2.1” x 2.9” x 0.5” 3x - 4-40 or M2.
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inputs to the power chips not the actual output voltage. It is possible for the power chip to be in safety shutdown while receiving an input signal. Thus it is possible for the LED to be lit while no voltage is output from the power chips. Note, it is possible and often prudent to code and debug the Arduino application with no battery connected to the MegaMoto using the LEDs as visual indicators. The LEDs are powered by the Arduino outputs and do not require a battery connected to the MegaMoto.
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output of the connected sensor outputs properly reflects the current through the bridge in either direction. A close up of the SENSOR jumper block is shown in Figure 3. Figure 3. Current sensor jumper block When operating in H-bridge mode the jumper shown in red above may be placed to link the current sense outputs of both chips. A second jumper chooses which Arduino analog pin to connect to this combined signal.
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3. Application Configurations When connected, as an H-bridge the MegaMoto is suitable for driving DC brushed motors both forward and reverse with variable speed. It may also be used to drive other bi-directional loads such as Peltier junctions, bi-directional solenoids, electromagnets and other DC loads. Pulse-width modulation may be applied to the inputs of the MegaMoto to vary the average voltage applied to the load. Thus the MegaMoto supports both variable speed and direction of a single load.
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PWMB Current Sense D3 A0 Bridged Timer2 PWM2B Both halves of the bridge report current on A0 H-Bridge mode is the most common configuration for driving DC motors. It allows each MegaMoto to drive one DC motor in forward and reverse with variable speed. Each Arduino base unit can support up to three stacked MegaMotos and hence three independently controlled motors. Dual Half-bridge Mode Example Figure 5.
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Figure 6. MegaMoto ganged half-bridge mode Function Enable PWMA PWMB Jumper D13 D11 Jumper to D11 Current Sense A1 Notes Pin D13 is used to enable the MegaMoto Timer2 PWM2A both the A-side and B-side chips must be driven from the same signal source or there will be a momentary short from chip to chip when they switch at slightly different times. Current monitoring is done on only the Bside chip. So the current read is ½ of the total current. Either A or B-side current can be monitored.
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The MegaMoto features a current sense output from each half-bridge power chip. This output is a voltage proportional to the current flowing through the chip. The voltage output is approximately 0.075V per Ampere of current. When jumpered for individual current readings the CA and CB outputs reflect the current passing through the M1 and M2 motor terminals respectively. When jumpered for combined current output the CA output reflects the combined current flowing through both power chips.
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As with the Enable input, it is possible for multiple MegaMotos to use the same PWM source. For example, if two motors always operate together, identical jumpers for Enable and PWMA/B can be installed on both MegaMotos. This obviously saves pins and allows more motors to be controlled from a single Arduino. In fact, there is no real limit to the number of MegaMoto units controlled in this way. The three MegaMotos per Arduino limit is only for completely independently controlled loads.
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Further if two different voltage sources (batteries or power supplies) are used, say one to power the Arduino and one to power the MegaMoto, it is imperative that the connection between the negative terminals of the voltage source be lower impedance than that between the Arduino and the MegaMoto. This is to prevent a ground loop between the Arduino and MegaMoto, which can destroy either unit. See Figure 7 for an illustration of this.
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6. Warnings The following warnings should be heeded when using the MegaMoto to avoid failure of the device: 1. Bench type power supplies do not tolerate regenerative current i.e. current flowing back into the power supply. Often their voltage will increase until the extra power is dissipated. If the MegaMoto is operated at 24V with a power supply of this type it is possible to exceed the maximum rating of the device and destroy the power chips.
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7. Dimensions and Mounting 8. Schematic The MegaMoto schematic may be downloaded from the Robot Power Web site. www.robotpower.com/downloads/ 9. Further questions For questions not answered by this document or for application advice please feel free to contact us. We’ll be happy to answer your questions and hopefully together we can make your project using the MegaMoto a big success. You can contact us at the following address: Robot Power 31808 8th Ave. S.
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Disclaimer: The MegaMoto is intended for educational and experimental uses. It should not be used in applications where human life or health or significant property value depend on its proper operation. Robot Power is not responsible for any loss or damage incurred by the operation or failure of this unit. We make no claims as to suitability or fitness for any application or use. The specifications listed for the unit are accurate to the best of our knowledge but are not guaranteed in any way.