Wednesday, September 24, 2014

Door-actuated space heater power lockout

Here's a little project I did last night:

Power strip modified for dry-contact switching

Magnetic switch on the door
I'll try to keep this short: due to some insulation issues in the garage under the second floor, Henry's room gets kind of cold in the morning.  This is not compensated by the house thermostat because it's in our room and we sleep with the doors closed.  So we use a little electric space heater to regulate the temperature in Henry's room at night.  With this comes a couple of problems:

  • Heater can be left on in the morning
  • If the door is open, the heater then runs open-loop and tries to heat the rest of the house 
  • The heater will run all day long, if it's set to even 1 degree above the "house" temp.  
  • This costs over $.25/hour
  • It's also (more of) a fire hazard since the heater will potentially be running when no one is in the house
I thought of a bunch of different ways to solve this problem.  Sure, go ahead and tell me about how the best way is to "turn the heater off when it's not needed".  Great, it's not going to happen. The next option I picked is the one that, to me, made the most sense.  Basically the heater power is disconnected when the door is open.  Since the door is always left open during the day, the heater won't run, and even if the door is closed, it's fine since the heater won't run "open-loop" (indefinitely).

To do this I modified a power strip and replaced one of the outlets with a 20A solid-state relay.  These relays are crazy - totally isolated and able to handle a lot of load. Since there aren't any moving parts, they don't wear out and you can switch them with very little current.
Solid State Relay

I wired two of the power strip outlets to the "load" side of the relay, and then installed a 9v battery and some contacts to the side of it.  Then I installed a magnetic switch on the door which will switch the 9v to the control side of the relay.  I was really careful to do everything really cleanly, since this is going to be in my kid's room.  (Don't want some wire  to come off and electrify the power strip case to 110v or something). So it took a couple of hours to build, but I am really happy with the result. It's almost invisible in the room and it works like a charm.

Got a new car

Well I did it.  Bit the bullet and, after thinking about lots of different possibilities, decided to go with what I know:

2013 VW Golf TDI with tech package.  It took me a while to find one, but as I learned from my last car, if you don't get what you want the first time, you'll spend the rest of your ownership trying to add it (and in many cases you still won't get it).

Here are some of the many features:

  • Heated seats (my previous car didn't have this and I regretted it for 12 years.)
  • Xenon headlights with "follow" action
  • LED DRLs
  • 17" rims
  • Dual power seats
  • Nav, SDcard slot
  • Bluetooth smartphone integration
  • Sunroof
  • DSG transmission (basically a standard transmission that is robotically automated)

It's going to take me a year or two just to get a handle on what is in this car.  I apparently have the RNS315 radio, which is different from the RNS516, but is apparently now standard on the tech package, I'm guessing because it's a little cheaper(?). This is the kind of stuff I am dealing with.

The only mod I've done so far is to rewire the lighter outlets so they are "always hot".  The new VW's have apparently finally gone to the dark side of shutting off the 12V outlets when the key is off.  It was driving me absolutely bonkers because every time I turned the car off my phone would reset, not to mention the fact that the battery wouldn't charge unless I left the ignition on.  I don't understand how the rest of the world can tolerate this.  My guess is that all the car manufacturers have gone to this standard because a few people managed to keep killing their car batteries, or starting fires.  Luckily it was pretty easy to rewire - no cutting wires, soldering, or even removal of any trim.  I am thinking about putting out a kit on eBay in case anyone else wants to do this.  If this sounds good, please let me know so I can gauge the interest level.

I'll be posting in the future with more details, but here are my (really) early impressions:

  • It's fast, but laggy (stomping it from stop = almost 3 seconds delay before launching)
  • Handling, on the other hand, is amazing - responsive yet very refined
  • Car tech has come a long way in the 12 years since I bought a car.
  • God help me if I ever have to fix this thing.
And for anyone who has this question on their mind, no I'm not planning to convert it to run on SVO. 

My 2002 Golf is for sale. It is clean, and, of course running the best it ever has.  I will miss it (almost as much as I will miss not having any car debt).  But I will have a LOT more free time.