HomeLink HA Interface #5 - Ooops!

I decided to get back into putting the interface together and finishing out the prototype.  I also decided to pull it apart from the breadboard and put the hardware onto an Adafruit perma-proto board that would interface directly to the RPi0W.  Little did I know that I would make a strategic mistake.

First of all, I pulled up Fritzing and put the wiring up on the board (visually) as shown:

As shown, I added three red LEDs to be able to pulse as a visual reference when the HomeLink channel is selected.  I also place a 7805 power tab in the lower right hand corner of the board.  If the board looks weird it's because it is the size normally used for a regular sized RPi.  And yes, it does overhang.  The 5 lines are actually a cable that goes from the breadboard to the LiftMaster.  These can be seen in the following images:








The Ooops in the title stems from the fact that when I applied power (9v to the breadboard connector) I encountered the following:

1. while the RPi0W was booting, I tried out the clicker with the LiftMaster and it was working fine
2. the bootup of the RPi0W seemed to be going fine, then it rebooted, and then rebooted, etc.
3. I reached over to turn off the monitor I was using and burned my finger on the 7805 poking up from the breakboard
4. I went and got my temperature laser reader and when I rebooted the RPi0W I was reading in short order about 150 degrees Fahrenheit.  Way too much current was being drawn.

What I have since surmised is that the peripherals that I had plugged into the RPi0W were drawing way more than the 1 amp max the 7805 could handle.  So what I plan on doing is removing the 7805 and replacing it with a 5v 2.5a supply that plugs into the RPi0W connected with a step up converter to push 9v to the LiftMaster which only draws 40ma.

HomeLink HA Interface #4 - Slowdown to use a breadboard

So life happened again.  I wish I could just get down with development and not have to stop for something, but that is never the case in my life.  Maybe when I am retired it will get better; hopefully more time available for my hobbies.  Right now I am in the middle of a kitchen update and work activities that are ramping up again.

I decided to go ahead and get a couple of Raspberry Pi Zero breadboards to see if I can solder the required resistors and the level shifter, along with a couple of breadboard electrical connectors.  I have it in mind to run power to the RPi breadboard and then connect the 850LM to the breadboard as well. That way, the power goes to one location and is distributed from there.  It would be nice if I could find a simple board that provides 5v power without being huge.

That being said, I fritzed a layout using the Adafruit quarter proto-board.  I used pretty much the same connections, except that I purposefully put most of the power traffic cop on the proto-board.  So there are now five entities that will need to go into a 3D print, counting the LiftMaster 850LM.  The fritzing layout (not showing the 850LM) follows:

This was pretty much as simple as I could get it.  I am using a slightly different Buck-Converter than the Adafruit one shown in the Fritzing diagram, but the principle is the same (9v -> 5v power for the RPi Zero W).  I am assuming at this point that when the relay switches and drops the voltage to zero that the 9v power will not drop below the point where the RPi will "brown out."  The resistors are 220 ohm which will give a draw of 40 ma from the 9v power supply during the relay switch. Note that the 850LM channel 1 is tied to GPIO4, channel 2 is tied to GPIO5, and channel 3 is tied to GPIO6 on the RPi Zero W.  The fritzing RPi is a Zero but that is okay for illustration purposes since the GPIO pinouts are the same.  The use of a RPiZW is for wifi access in my IOT vlan.

Getting Back to the Blog

I have been noticeably absent from writing on this blog for some time.  I have been taking an online class for the ISSEP concentration for my CISSP security certification.  Now I am going to have some time to come back and attack some of these projects that have been put on the back burner.

Update: I was fortunate enough to have passed the ISSEP examination.  Now I have to go through the endorsement process with a new updated resume and a different outlook on life.  No more working on certifications for a while!