Version 1.0 - May 26, 2011
5
Battery Inputs: The Wasp requires an external battery connected to the battery positive and
negative terminals. The positive terminal is marked with “++++” on the silk screen of the unit.
The polarity of the battery input must be respected. Reversing the battery connections can
damage the unit.
The Wasp does not require external filtering or voltage regulation. It may be used directly with
a 6V-28V battery or other voltage source. Connections can be made using either the optional
screw terminal or by direct solder connection.
RC Cable Connections
The Wasp commands are sent to the unit over a standard hobby RC servo lead. This is a
three-wire connector exactly like those used by servos. The Wasp expects a standard RC
servo command pulse stream as well. Many Internet resources are available which discuss
this command format and most microcontroller function libraries will contain functions suitable
for controlling the Wasp. All recent vintage RC receivers should be compatible with the Wasp.
Normally the on-board 5V regulator of the Wasp is connected to the center wire of the RC
cable. This allows the Wasp to provide power to an RC receiver or other 5V-powered device.
If the device doesn’t need that power or has its own internal 5V supply the center wire of the
RC cable should be pulled from the housing or clipped off to disconnect it from the outside
source. This allows the internal regulator to power the Wasp CPU and MOSFET circuits but
disconnects it from the outside supply.
Other Connections
Calibration Contacts: Two contacts are provided on the unit to initiate an RC signal
calibration. Shorting these contacts using a small bit of wire or other conductive material
activates the calibration function. Here at Robot Power we use fine tipped tweezers for this.
See the calibration section above for details on how and when to calibrate the Wasp.
Limit Switch Inputs: These connections are optional. The Wasp will function perfectly well
with nothing connected to these contacts. The purpose of the limit switch inputs is to stop
motion of the motor in one direction but not the other when one of the switches is closed. For
example imagine a load being driven along a track with the limit switch mounted at the end.
When the load hits the end of the track and closes the switch the Wasp cuts off the motor in
that direction. The load may still be driven in the other direction to move away from the switch
and the end of the track. As soon as the switch opens the motor may be driven in either
direction again.
The limit switch inputs are considered “open” when they are unconnected or when driven to
logic high (5V). Similarly they are considered closed i.e. activated when the input is driven
logic low (0V). The three limit switch connections as shown on the above diagram provide
connections to the two switch inputs and to a 0V connection. Thus the limit functon can use a
2-wire cable to connect a switch between the limit switch input contact and the common 0V
contact as shown in the diagram.
4. Circuit Features
The Wasp uses the Infineon BTN7960B as its power-switching element. This chip contains
two low-resistance complimentary MOSFET switching transistors along with protection and
driver circuits. Each BTN7960B contains a complete half-bridge and all needed driver circuits
including robust protection features. The device features self-protection from over
temperature, over current and over and under voltage conditions. As mentioned above the
two half-bridge chips are connected as an H-bridge.
