I recently had the need to have a doorbell at the entrance to my property, having recently put in automated gates. I could have run a cable, but I wanted to try out some new 433 MHz transceivers I recently purchased. The entrance would have a push-button switch and the house would have a receiver accepting packets from the entrance. Once it got a packet, it would trigger a relay to ring the doorbell. The doorbell was an old model, driven by 12V AC, so I thought a relay would be the handiest way to triggger it’s chime. Also, attached to the internal Arduino would be the old doorbell, connected to a gpio input which could also trigger the relay, activating the doorbell. Two methods to chime the same doorbell.
Category Archives: Tutorial
Over the last while I’ve been having a problem with excess humidity in the shower rooms. Imagine that, the builder never put in extractor fans when the house was built! Anyway, I could put in those fancy extractor fans with the built in timers or humidity sensors, but I decided to do things the more interesting way, by using a small computer to read the values from a humidity sensor in each room, and based on the readings, turn on the fan until the humidity was reduced to an acceptable level.
Here’s my latest DIY project, a smartphone based on a Raspberry Pi. It’s called – wait for it – the PiPhone. It makes use an Adafruit touchscreen interface and a Sim900 GSM/GPRS module to make phone calls. It’s more of a proof of concept to see what could be done with a relatively small form factor with off-the-shelf (cheap) components. I don’t expect everyone to be rushing out to build this one, but I had great fun in doing it, as it builds quite nicely on my previous projects, especially the Lapse Pi, a touchscreen time-lapse controller, and uses most of the same hardware.
So here’s my latest Raspberry Pi project. It uses the PiTFT Mini Kit, which is a 320×240 2.8″ TFT display and Touchscreen from Adafruit Industries that fits neatly onto my Raspberry Pi, to control a user interface to drive the back-end time-lapse script I showed you in a previous blog article.
(DISCLAIMER: Not meant as a security solution or a lesson in good dog behavior. It’s an experimental proof of concept to play with the application of embedded computing to solve particular use cases)
Sleep deprivation has been driving me mad recently. And it’s all down to a new member of the family (kind of), our new dog. She barks at night when she’s left out. She barks early in the morning when she’s left in. So once I recognized the patterns of her barking, I realized that all I needed was something that would let her out when she needed to go for a pee, usually around 6:30 in the morning. I could do this with a timer switch and a door strike, but where’s the fun in that.
I’ve recently had the need to solder some small components at home, but don’t have a microscope, or even a decent magnifying glass. But then I thought that I’d a rather expensive DSLR and a pretty good macro lens, along with some extension tubes (allows closer focussing). Now I know that the camera has a Live-View facility (it’s a Canon 5D Mark III), but would the display be output easily to a monitor? Well, in the box that came with the camera, I found a cable which had a composite connector and some kind of A/V connector for the camera, so I set it up as shown in the pictures, a switched on the camera. The menu was displayed on the monitor, as hoped. Once I’d enabled live view and adjusted the settings so the exposure was OK, I zoomed into the display, first x5 and then x10. Each time the live view display was replicated on the monitor.
Here’s how to add a 9-pin serial port to your Raspberry Pi, and it’ll only take you 10 mins. Well, maybe a couple of weeks to wait for the part to arrive from Hong Kong, but once it arrives, it’s only 10 minutes! 😉
Here’s the part you’ll need. It’s an RS232 to TTL converter module containing a MAX3232 chip. The MAX3232 is important, as the older MAX232 won’t handle the 3.3v levels of the Pi, whereas the Max3232 will. It comes with a 4-way cable for connecting the module to the GPIO of your Pi. If you search on eBay for “RS232 Serial Port To TTL Converter Module MAX3232” you should find several. The one I got cost me €3 with free shipping from Hong Kong.