A forum user has raised a question about his BellMote which was not working and as a result I realized that I might have shipped some BellMote kits without fixing a PCB glitch that I had on that batch of PCBs. Namely there was a trace missing on the PCB, which can be fixed by soldering a short hookup wire between these 2 points (red wire shown):
So my apologies for missing that in some kits. If you have one I would hope you are able to add the missing wire, or I can do it for you and I can test the BellMote to ensure it’s working if you’d like to return it “for service”. I guess they call that a recall in the auto world. Feel free to contact me if you have questions or concerns about this specific issue.
I am quite happy to announce a few new products (or new revisions), some of which people have been asking for a long time, now finally available at the shop!
First there is the IOShield which is now available as an assembled PCB with optional “24VAC input package” which allows you to place it in places where you have 24VAC input, like I did in the wireless sprinkler controller project.
Then there is a small BellMote run with OSHPark purple PCBs. Completely automate your doorbell with this kit which allows you to detect, trigger, and disable your doorbell, all wirelessly via Moteino gateway.
Next up is the SonarMote which finally has a new revision (R2) which addresses some bugs, has a simpler BOM and is even lower power – just 10uA average when the Moteino is properly slept – sample sketches here. A wide range of applications are possible, from parking sensor, inventory control, sump pump monitor, and others.
Finally we have the MiniBoost which is a small SIP form boost regulator that yields 5V from an input voltage of 2-4V. Up to about 1A is possible from a charged LiPo battery (4V) and will easily carry a moderate load like a RaspberryPi. It uses the same boost regulator as the MightyBoost but the SIP size makes it very versatile for breadboard projects. It’s perfect for projects where you have a main working voltage of 3.3V but you have some sensor that needs a hefty 5V source. Comes with onboard green power LED. It has is the same pinout and size as the legendary 7805 regulators:
It takes a long time to go through prototype stages and then manufacture electronics of high quality, all as a small operation like I have. I hope to get more time to put more documentation and assembly instructions together for these kits and boards. Some of them have already been introduced as prototypes and have a fair amount of information available. There are also other things I’d like to blog about, just not enough time, stay tuned for more!
The last BellMote prototype ended up having 2 LDO linear regulators, 12V and 3.3V feeding from the 12v one. I was split on using LDOs going forward. The upside is they are cheap, even 2 of them are under $2. The downside is they are inefficient and run warm/hot depending on the load. I could have gone with a single 5V LM7805 which will run even warmer, the higher the gap between Vin and Vout.
Digikey-ing around, I found these two switching regulators that are drop in SIP replacements for any LM78xx series LDOs: a RECOM 0.5A output with 7-28v input range ($2.8), and a Murata 1.5A 7-36v input range ($4.25). I tried both, and below are the results:
I won’t repeat the captions here but the clear winner is the Murata (plenty stocks at Digikey) it’s quite a bargain given the advantages. I tested it on 24VAC as well and it does not heat up at all either so it will be perfect for some coming interesting projects I have in the works that will feed on 24VAC. The RECOM regulator is just $2.8, still good enough for 16VAC but I prefer the Murata for further 16-24VAC powered projects. That said, I will offer these for sale (2 of them, one RECOM, one Murata, and I will replace the LDOs with a Murata and keep the third one). I may make a kit of this, not sure yet. For now you can grab these two from the first prototype batch, they will be worth millions when LowPowerLab is like Apple and me like Steve Wozniak 30 years from now (-:
UPDATE: I eventually decided to use a single switching regulator that I found on digikey which is both awesome and well priced. See this blog post update about it.
My first DoorBell Mote prototype was working nicely and it allowed monitoring the door bell (while also triggering it remotely – toddlers love it). But I wanted more. On weekends the family likes to get a well deserved nap during the day and often those pesky solicitors ring the bell and wake everyone up. So naturally the doorbell has to be disabled also, without major effort or any disconnected wires. Sounds like the perfect addition to the Door Bell Mote. So I made a new revision and a proper PCB for this, below is the schematic with the changes and the proto PCB from OSHPark. Actually I made more changes to the schematic after putting together the PCB, so there are some differences. I’ve tried a LTV814H optocoupler for AC detection instead of the more expensive H11AA11, it works just as well, but both can be used on this PCB:
There are 2 regulators on this PCB. One is a 12V linear LM7812. The second is a 3.3V linear regulator getting input from the 12V LM output, both in TO220 packages. I know they are super inefficient to convert rectified 16VAC to DC voltages and the critics will stone me for doing this. But here’s the deal – the linears are about 50cents each and I had both among my junk parts. An efficient switching regulator is somewhere between $5-$10. The linears run somewhat warm. The 3.3V regulator only gets warm when I use the disable relay. So they can get warm but not hot, which is fine by me, it’s just a tradeoff. I might make a new revision where I have a single switching regulator such as this one, a drop in replacement for the LM linear regs. Continue reading
UPDATE: Check out the new version of this, now with bell enable/disable function!
A lonely doorbell activated by a boring push-button at the front door is not very exciting in a world of Arduino and “Internet of Things”. I’ve been wanting to Arduinize the doorbell into the Moteino Framework gateway interface so that I could:
- observe/count/graph when the doorbell is used
- get notified when someone rings it if I am not at home (email, SMS etc)
- play a sound when I am in my lab where I have a hard time hearing the chime (did I hear it or not? should I go upstairs to check? nah… I’m too busy for that)
- ring the bell if I want to, *remotely* from your mobile device (why not right? just detecting is too boring)
Below is a schematic of what a typical wired door bell circuit looks like, and also a photo of what it looks like in my house. The dotted green rectangle is the circuit that I have physical access to – pictured next to it in my basement (and I don’t have a back door button):
I have a single button (front door) and probably most houses do. So I only care to inject my solution for that front door button. There is typically a 16VAC transformer powered from mains that activates the chime when the switch is pressed. So there are a few issues to solve in order to tap into this circuit, detect button presses and also being able to control it via Moteino:
- Power our circuit from the 16VAC doorbell transformer. This is a good exercise to create a DC power source from an AC source. We’ll use a simple half wave rectifier to achieve this
- Detect when this 16VAC current flows through the wire coming from the outside button. When the button is pressed, the chime will ring and our circuit detects the AC current and outputs a digital HIGH for the Moteino input pin that monitors it
- Make the Moteino “press” the door bell button when it receives a “RING” wireless message
I will explain these points step by step. Let’s get to work! Continue reading