Servo - August 2016

the code. We checked the board, saw that pin 9 was denoted as RX and pin 8 for TX, and entered those numbers.

It struck us as way too easy. The program, however, compiled without incident. We uploaded the program and opened the serial monitor. The serial monitor declared that the board was unable to connect to the Wi-Fi.

That struck us as strange. We had no problem connecting to Wi-Fi with the previous demo program. Fortunately, the Blynk forum is a comprehensive resource for all things troubleshooting, and we were eventually able to discover the problem (though it had us feeling a little silly). The Wi-Fi shield was having trouble connecting to the Internet because we had pushed the shield farther down onto the Uno, and the interference with the Wi-Fi antenna was as effective at messing up our Internet connection as was someone using the phone when you were using a dial-up connection.

We gave the shield a little more breathing room, and the serial monitor no longer mentioned being unable to connect to the network, but gave a different problem instead. The serial monitor would give the cryptic message “Failed to disable echo.” After returning to the supremely helpful Blynk forums, we found the solution to this problem too. We had incorrectly designated the RX and TX pins in the program. Even though we went with the numbers as they were printed on the board, in the program those numbers actually have to be reversed. That’s not to say the RX and TX pins as labeled on the Wi-Fi shield are wrong — the issue boils down to a difference in definition — RX and TX with respect to which device? In any event, swapping the pin numbers put us in business.

We uploaded the fixed program and watched the serial monitor with anticipation like what Marty and Doc Brown must have felt as they exited the DeLorean to see whether they really were taken back to 1955. The line “Connecting to the network” hung on the screen for a few agonizing seconds before the monitor confirmed that we were, in fact, connected to the Internet. We started the Blynk app, tapped the onscreen button, and when the claw jerked to life we felt a feeling of triumph like what George McFly must have felt when he knocked out Biff Tannen.

Each tap of the button would only open the claw a little bit, so we went back to The Grid and made a new interface using a slider. The slider opened and closed the claw like a dream, and it showed impressive sensitivity.

And with that, we had inducted a robotic claw into the Internet of Things.

Rover Phone Home

A claw is cool, but we wondered how effective the Blynk app (normally intended for traditional Io T functions like activating a light or something like that) would be for controlling a robot. We rigged up a simple driving base using two servos to power the wheels, but the Uno (or Wi-Fi shield) couldn’t accommodate both because there was only one 5V pin. So, we busted out the SparkFun PWM shield which comes with a whopping 16 PWM channels.

We soldered on some stackable headers and some female headers for a few PWM channels. We wired up the servos, stacked the shields, and soon had a super simple rover eager to join the Io T. We set up a control panel with Blynk using two sliders, and turned it all on.

It was not exactly to the point where we feared we would have to dispatch a blade runner to track down and retire it. The servos jerked a little bit, but were not really responsive to the controls. We think the problem is that the setup was a little too power hungry. We were running it off of the wall power as recommended to increase the stability of the wireless connection, but power requirements are a big consideration when stacking more than one Arduino shield. The Wi-Fi shield is one of the more power hungry shields to begin with. The PWM shield — sourcing 5V pins out the wazoo — is also a member of the power hungry club.

However, that doesn’t take away from the awesomeness of the ease with which we connected the Actobotics gripper to the Internet. The SparkFun Wi-Fi shield and Blynk provide very promising (and affordable!) platforms for initiating robots into the Io T.