September 27th 2020: Orange County Florida COVID-19 Report

It’s September 27th, 2020, how is Orange County Florida doing with COVID-19?

The rate of decline in new cases had grown sluggish at the end of August, plateaued and then had a slight rise in September.   Orange County is averaging 147 confirmed new cases per day over the last two weeks, compared to an average of 14 new cases per day in the first two weeks of April, so the number of people infected each day is still about 10 times higher than in April.

(You can ignore that 7 day hump at the beginning of September….a large lab reported a backlog of positive tests all at once.)
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Getting IOT devices / Geeni Smart Plugs working with OpenWRT / dd-wrt

After moving my wifi router to the OpenWRT firmware, my Geeni smart powerstrips were authenticating to the wifi router (I could see their MAC addresses) but not communicating properly (the device name was a question mark, and nothing could communicate with them).

The secret was to turn off WMM mode (Wireless Multi Media) and then they all immediately started working again.

The firewall gets in the way of HP printer device discovery, so you may need to assign the printer a specific IP address and then manually add the IP address to your clients.

HP Device Manger -> Setup -> Network/Ethernet/Wireless network. Then click Advanced Options, choose Manual Discovery, and type the IP address.

Insulation & heat loss of my DIY cooler

My DIY TEC Cooler has an interior volume of 480 cubic inches (6x8x10) and an interior surface area of 376 square inches (2.61 sq ft). It has an exterior volume of 1.55 cubic feet (12x14x16) and an exterior surface area of 1168 square inches (8.11 sq ft).   It generally has 3 layers of 3/4″ poly-iso insulation (R5) plus a small amount of one-part urethane expanding foam (say, R2?) in some areas, for an estimated R 17 insulation value (sorry, I’m using imperial units here as my insulation comes with R values….)

To calculate the amount of heat that will escape from inside my cooler to the outside (the amount of heat loss I need to counteract with the TEC system to maintain a set 34°F temperature on a 77°F day), we need to know the thermal delta between the inside and outside of the fridge.   (I’ll use 34°F for a good refrigeration value, and 77°F for the exterior temperature).

I’ll also use the average value of the interior and exterior surface area ((2.61+8.1) / 2) = 5.36 sq ft for this calculation. As a reminder, the equation to calculate heat loss in BTU/h is:

equation for calculating heat loss in btu/hours

In imperial measurements:
[5.36 * (77-34) ] / 17 = 13.55 BTU/h

13.55 BTU/h   divided by   3.41 = 3.97 watts

Using the SI system with things translated appropriately gives similar numbers:
0.49796 (25-1) / 2.99 = 3.99 watts

Of course, the above numbers may be completely incorrect, so I also did an experiment after building the cooler:

At 4:45pm I placed 3 refrigerated 12oz (355ml) cans of generic Dr. Pepper in my homemade DIY cooler with a temperature of 3.8°C.   [The active TEC elements were turned off, as I was just testing the insulation properties.]

At 4:21am the next day (11 hours 36 minutes later, rounded to 11.5 hours hereafter) I opened the cooler and one can, measuring the interior temperature at 14.6°C. [we’ll assume all three cans gained the same amount of heat…I only wanted to drink one can.]

So, 36 fl oz (1065 ml) of (basically) water gained enough energy to raise its temperature 10.8°C in 11.5 hours. The specific heat of water is 4.184 J/g-K. 1065ml = 1065 grams of water, or just about 1 kg. Nice how that works out.

4.184 J/g-C * 1065 g * 10.8 C = 48124.3680 Jules = 48.124 kJ = 0.0134 kWh = 13.4 Watt/hour

13.4 wh / 11.5 h = 1.1652173913 watts of continuous energy transfer from the outside to the inside of my cooler (heat gain, or cold loss).

You might notice that the calculated 3.9 watts is not equal to the observed 1.16 watts.
The main reason for this is that the interior of my cooler was never at 34 °F. It started at 3.8°C (39°F) and then raised up to 14.6°C (58°F) over 11.5 hours. It spends more time a higher temperatures, as the rate of heat transfer decreases as the thermal delta decreases. [Also, the ambient temperature was closer to 71.6°F, so the difference between the interior and the exterior was significantly smaller than in my previous calculations.]

For example:
[5.36 * (71-39) ] / 17 = 10.09 BTU/h / 3.41 = 2.95 watts
[5.36 * (71-58) ] / 17 = 4.099 BTU/h / 3.41 = 1.20 watts

However, the integration of the above numbers over 11.5 hours would still give me more heat loss than I observed. So either my experimental measures had a flaw, or the R value of my cooler is higher than the estimated 17.

However, as the results are of the right order of magnitude (4 watts vs 1.1 watts), I’m happy with my calculations and the experiment, and feel that the 4   watts of cooling power needed to maintain a 34°F interior temperature is a good upper bound on the performance needed by my TEC system to maintain temperature.

Moto X4 power button failure (part 2)

Remember how my Moto x4 had a power button failure after 10 months of ownership? Well, the replacement x4 phone that Motorola shipped me had its power button fail in the same way after only a month of usage. Luckily, I still have a month of warranty coverage, and their customer support representative again waived the $24.99 “Premium” fee to ship me a replacement phone before I ship them back the broken one (with a $200 deposit.)

However, I’m not at all impressed with the hardware quality of the power button on this model. I think I will have to just set the screen timeout to a small number of seconds and stop turning the phone off with the power button. (It already has a swipe to activate feature so you don’t need to use the power button to turn it on…)

Installing Garage Door Slide Locks

My garage has four doors (two in the front, and two in the back) which gives a lot of cross-ventilation potential, but unfortunately some of the doors had the slide-locks installed incorrectly, such that there was no available slots to lock the doors in a “slightly open” position to let air circulate.   They also only had one lock per door, so I rectified that situation by adding a 2nd slide lock to the other side of each door, and moving a few of the original slide locks so that two of the doors can be locked with a 2″ gap below them.   I spent less than $30 for all four slide locks and a box of self drilling sheet metal screws, so it was a relatively quick and inexpensive improvement.

Banshee sailboat rudder & tiller rigging

This is my new (to me) Banshee sailing dinghy. She is 13 feet overall, and cat rigged, which means she only has a single sail behind the main mast, with no head sail. This rudder and tiller doesn’t look exactly like that shown in photos online of other Banshee boats, so it may be a later retrofit.

This is how I rigged up the rudder and tiller. All of the attachment points were already there when I got the boat, but I added two bungee cords and an up-haul line. I have no idea if this is the “official” method, but it seems to work for me.

First, I wrapped a 24″ bungee around the tiller and secured it to this forward eye strap with a chain link and then attached it to these pre-existing eye straps on the inside of the transom. This gives an automatic “return to center” action for the rudder.

I used a 42″ yellow bungee cord wrapped in the middle around an existing bolt
in the front of the rudder to pull and keep the rudder down, while at the
same time, allowing it to rotate backwards if ran aground.

I attach the ends to this front eye strap when under way, or can move them
to this rear eye strap to make the rudder easier to lift.

I used a 1/8″ line tied to an existing hole in the back and of the rudder and routed around the tiller to a bottom mounted jam cleat to raise the rudder. It’s certainly possible that this jam cleat is really intended for a down-haul line, and not an up-haul line, as it’s on the bottom of the tiller.

So, that’s what I’ve done, it works for me, but feel free to leave a comment if I’ve completely messed things up.

Philips Norelco QT4085 beard trimmer disassembly and battery replacement

My trusty (yet old) beard trimmer has needed to be plugged in to use for a long while now, but the batteries finally degraded so much (I suspect they were a direct short) that even plugging it into its charger failed to make it work. So, I took it apart and replaced the batteries. (They needed it, I believe they were from 2001.)

This video distills what I learned (the hard way) about the proper order of operations for disassembling this model to get to the battery to replace it.

NES Classic 500 in one game console controller pinout

I had to repair the cable on one of those “500 in one classic game consoles” that look like a mini Nintendo Entertainment System (NES) but don’t actually say the “Nintendo” trademark on them anywhere.
An example can be found on Amazon here:

The order of the wires inside the controller on the PCB (NES01-JOYV1.1) is (from left to right): orange(red), yellow, blue, brown, white

The pinout for the wire colors at the end of the cable is as follows: