Looking for a small, simple, RC on/off switch? This Pololu unit can dump 3A signaled from a simple R/C PWM signal!
This tiny board from Pololu takes a standard RC PWM signal and does a simple on/off toggle of a low-side mosfet that connects/disconnects your load's ground line. It's smart too, with diagnostic and data lines & LED that check for the presence of a valid RC signal (10-100 Hz pulse rate, 0.5-2.5 ms pulse width), and what state it is presently in. When the PWM signal goes above 1.6mS, it turns on. That simple!
What is it used for?
It's so small and light, it can be used in regular RC aircraft applications to activate lighting systems or other small (under 3A) loads. It's also plenty strong to drive a relay for even more power driving capability. Or use it in a microcontroller project where it can't interpret a PWM signal, and use this to convert the PWM to a simple logic signal.
This really is small. It's just 0.4" x 0.6" and weighs just 0.5 g (0.02 oz) without the included header pins.
Hook up your input signal. Look at the first image, bottom left corner, where "RC IN, VRC, GND" are. This would be your standard RC "Gnd/Pwr/Signal" pinout ready to take your input. You can easily solder on a regular servo wire to these points to make plugging into a breadboard (with double-ended pins) or RC receiver easy.
Hook up your LOGIC Power. Logic power simply powers up the board - not the load! The bottom RIGHT side of the same image shows "Vcc/Gnd". Vcc and Gnd are your power connections for LOGIC. If you want to power the logic board from the same power as coming in from your RC source (which is generally what you want to do), flip the board over and solder bridge the VCC and VRC pads (circled with red on the image). These are on the bottom middle of the backside of the board. Simply dump solder onto these two pads until they bridge together, and your switch will then get its power from the the VRC line.
If the connection between the two power pins is not made, VRC can be left disconnected since it is not used by the RC switch board.
Hook up your LOAD Power. This would be the separate battery you would want to use for powering your load. For example, a set of AA cells powering a high-intensity LED array. This is shown on the TOP LEFT and RIGHT sides of the FRONT of the board as "Load Supply" (twice), and on the other side "MOSFET OUTPUT" and "GND".
Using the example above of an AA battery pack and LED array, you would hook the (+) of the battery pack to one of the "Load Supply" lines on the left, and the (-) to the GND pad on the right side of the board.
The VCC pin can also be connected to the load supply by shorting across the pads on the back side of the PCB marked by the yellow box in the picture to the right, allowing either the load supply to power the digital device or allowing the digital system to power the load.
Hook up your LOAD. Again using the LED example, you hook the LED array anode (+) connection to the other left side "Load Supply", and the LED array cathode (-) to "MOSFET OUTPUT". Note: LED arrays need proper current-limiting resistor sizing that is imagined into this circuit.
Monitor your switch. This switch has a "GOOD" and "OUT" pin you can monitor for status of the switch. The outputs will have the same voltage as the Vcc power input (2 to 5.5VDC).
"OUT", goes high (on) when a valid RC signal is detected and the pulse width is above the threshold of 1.6 ms. The "GOOD" output, indicates the presence of a valid RC signal (10-100 Hz pulse rate, 0.5-2.5 ms pulse width).
An LED on the RC switch indicates the status of the RC signal (and outputs). When a valid RC signal is not detected (GOOD and OUT both low), the LED flashes with a duty cycle of approximately 50% (i.e. the LED is on for as long as it is off). When a valid signal is detected but the pulse width is below the threshold (GOOD high and OUT low), the LED flashes at a very low duty cycle (i.e. very short flashes). When a good signal is detected and the pulse width is above the threshold, both outputs are high, the LED turns on (no flashing), and the MOSFET is on.
VCC is also the gate voltage that is used to turn the MOSFET on, so it should be noted that lower VCC voltages will lead to higher MOSFET on resistances (which in turn limits the maximum current the device can switch). The RC signal input pin, RC IN, can handle voltages from 0 to 7 V, and the threshold for a logic high is approximately 1 V. The MOSFET can tolerate voltages as high as 30 V, but the flyback diode is only rated for 20 V, so an external diode should be used for load voltages that can exceed 20 V.
A 12-pin 0.1" straight breakaway male header is included with the Pololu RC switch with small low-side MOSFET, which can be used to connect the RC switch to perfboards or breadboards.
|Size:||0.4 x 0.6"|
|Maximum operating voltage:||30 V2|
|Maximum output current:||3 A|
|Minimum logic voltage:||2 V|
|Maximum logic voltage:||5.5 V3|