Amazon Dash Wand

Amazon is running a promotion where you can buy an Amazon Dash Wand with Alexa for $20, and get a $20 credit on your account when you register it. (So if you are a prime member with free shipping, you get a dash wand for $1.30 in taxes.) It’s basically a handheld wifi enabled barcode scanner with Alexa voice input designed to get you to buy more stuff from Amazon.

The wand arrives in a small blue and black box, and is half white and half black. The black end shrinks to a rubber ring so that you can hang it up on the included sticky hook, and it has magnets hidden inside so you can stick it to your fridge.


To install the two AAA batteries (included in the box) the quickstart guide says “Open the Amazon Wand by pulling the two halves apart” when it should really say “Get two strong guys to play tug-of-war with your wand until the two sides pop apart”.

It requires you to have the Amazon app on your phone to pair the Wand with a (2.4 Ghz only) Wifi Network, which also links it to your account. After that, you can use the wand by pressing the button. A red light shines out the end, and if you point it at a barcode, the item will magically appear in your Amazon Shopping cart. (No wonder they are practically giving them away…)  You can also press and hold the button to talk with Alexa, to, for example, add an item to your cart that doesn’t have a barcode by voice.

Amazon music is not supported on the device (I suspect playing music would run the AAA batteries down too quickly, plus the single speaker isn’t exactly high quality), but some other Alexa skills are, so you can check on the weather or play colossal cave (although you have to push and hold the button every time you want to issue a command).  Home control commands (such as HUE lighting) is supported, so this could make a good secondary control device for a smart house. Messaging with Alexa is NOT supported. (Which is a pity, as it’s ALMOST small enough to wear like a  combadge.)

For a teardown, see this link.

T-Mobile DIGITS (android) app review

T-Mobile is offering a beta program where you can sign up for “Virtual” phone numbers, and/or use one number on multiple devices.

Basically, it’s a VOIP service that allows you to have one main (sim card) number on a device, plus one or more “virtual lines”, and then use their VOIP application (called DIGITS) to log into your account on any device and make/receive calls and send/receive SMS/MMS messages.

By default it allows you to “use minutes” to call in or out on your “virtual lines” which means that it redirects voice traffic over your regular phone number so you can use it even if your data service isn’t the best, (which would solve the “bad quality” VOIP issues I’ve seen with Freedompop), and it always sends messages via data. But, you can tell it to “use data” for voice calls, and go full VOIP (for example, on a wifi only device).

A select few Samsung phones have software built in that handles the virtual lines and VOIP calling, but for all other phones, you have to install the T-Mobile DIGITS application.

The concept is good, and the service works as it is supposed to, but the DIGITS application itself (at least as I tested it on a Nexus 6) has a few issues.

The first issue is that it burns through data like it’s streaming video. I’d accuse them of ex-filtrating data off my phone, except I don’t have anything valuable enough for t-mobile to try and steal. I suspect the application just has a bug somewhere that makes it check in with servers much, MUCH more frequently than it should.

For example, when using the service for a few days away from wifi, I racked up 320 MB of data, while IDLE. (T-mobile gave me extra data when I called to report this behavior, but I can see why it’s still in BETA).

Also, it refuses to work unless you have location services enabled. I guess this could be an enhanced 911 liability issue where they want to be sure to be able to give an accurate address to police if you call 911, but I already had to enter in my E911 home address just to activate the application. It seems like they could ask for permission to turn on location services if needed, and then NOT turn them on unless you called 911, as this drains the battery.

In addition to powering up your GPS all the time, the application itself uses a lot of battery power when idle in the background. (note, the graph below is just the application usage, and does not include the extra power sent to the GPS chipset to be always active…)

When you are using more data and more power than the Google App while sitting in the background idle, you know your app needs to go on a diet.

In summary, multiple virtual lines is an interesting and useful concept, but until the DIGITS app doesn’t kill your battery life and suck down your bandwidth when idle, I think a dual sim phone is a better solution for two phone lines.

Curtis 1231C-8601 500A PWM DC Motor Controller teardown

After replacing the Curtis 1231C-8601 motor controller that had failed, I opened the case up to figure out what had failed.  The controller hardware is inside of an aluminum extrusion with both ends “potted” with some black semi-flexible material (hard silicon perhaps?) that could be cut using a razor knife and a lot of effort.

Inside, there is a Pi shaped piece of aluminum extrusion that acts as the heatsink for the MOSFETS and freewheeling diodes, as well as being electrically connected to the motor – terminal. It is held against a large thermally conductive, but electrically insulating pad, which separates it from the controller case, but allows heat to be dissipated. It is held in place with 8 screws that pass through insulating plastic brackets into the bottom of the case.

People online had told me that these screw holes were “potted”, but on my controller they were just filled with two rubber plugs.They also told me that you could not cut through the Curtis potting material with a razor knife. [This super hard potting material was also prone to cracking at the edges and letting moisture into the controller, so a flexible rubber like material is better anyways…]

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Current imbalance with dual chargers – TSM 2500 / EVCC


This graph shows the temperature (in C) of my two chargers, as well as the watts of power they report providing over time (in minutes) as they charge the Nissan Leaf battery pack in my truck.

For the first 23 minutes of the charging session, both chargers are putting out 12.5 amps (at around 129.5 volts) or around 1600 watts. The 12.5 amps is limited by my MaxC (maximum current) setting of 25 amps total by the Thunderstruck motors EVCC (Electric Vehicle Charge Controller). So in the first 23 minutes, the amount of power drawn is limited by the chargers.

From the 23 minute mark until the end of charging, the battery bank begins to accept less than 25 total amps (because the cells are getting charged, and the pack voltage is getting closer to the MaxV (maximum voltage) that the chargers are putting out.

So for example, at minute 32, charger A is still supplying 12.5 amps (1600 watts), but charger B has dropped down to supplying around 4 amps (500 watts).  (The difference in power output also has an effect on the temperature of each charger, shown in the yellow and blue lines…) I have been having overheating issues causing my chargers to shut down, hence the detailed logging….

My hypothesis is that the power difference is due to one charger providing a slightly higher actual voltage (e.g. it’s voltage sensor reads just slightly less than the other charger) so although they both claim to be limiting voltage to 129.5 volts, one of them is actually putting out a slightly higher voltage than the other, which causes more current to flow from the “hot” charger to the battery bank.

This graph is evidence that the ThunderStruck motors EVCC does not do “active” balancing of the chargers. I suspect that the EVCC probably just sets the “maximum” amps and volts for both chargers and then turns them loose.

The chargers report back the amps/voltage/watts they are providing, so the EVCC could in theory dynamically change the maximum current settings on the “hot” charger to only provide an amp or so more than the “cold” charger, more evenly balancing the load. However, this would add complexity and require extra code and testing. And as you limited the current provided by the “hot” charger the “cold” charger would start providing the extra current, and over time the identity of the charger providing more current would switch back and forth.

This active balancing would only be needed (or be useful) when the battery pack was drawing less than the maximum current capacity of your charger array (near the end of the charging session, in the 80-100% SOC range).

The limited potential benefits to this added complexity could be:

  1. Your chargers (and wires) would presumably stay closer to each other in temperature (only really an issue if you are suffering from overheating, which is why I was logging this data in the first place).
  2. If your chargers are more efficient at a lower current, it could save you some energy / heat. (Conversely, if your chargers are most efficient at full current, it may be better to run one charger at full current and just use the other charger to “fill in” any extra current needs.)

In short, I can understand why the ThunderStruck motors EVCC does not perform active balancing (at least with the version of the firmware I’m using — v2.3.1), but I would certainly be willing to test a current balancing feature in future firmware releases.


JuiceBox EVSE Pro 40 – Second Unit


I’ve been using an Electric Motor Werks JuiceBox Pro 40 to charge the truck for the last six months. It worked just fine most of the time, but suffered from intermittent GFI trips that would cause the wifi module to turn off entirely (going offline and stopping the charge) very occasionally.  After flashing the firmware didn’t fix the issue, they sent me a replacement unit. (Pictured above).

You can read all about the old unit here. The new unit has a slightly newer version number (v8.14.07) and the power cable going out to the J1772 gun is shorter (looks to be 18′-20′ instead of 25′) and MUCH thicker (marked as 8 GA wires for power, which matches the wires used to supply my NEMA 14-50 outlet). I have some photos of the differences here:




Poking around the Electric Motor Werks website, the “thick” cable and gun appears to be what the current JuiceBoxes come with by default, but they have an option where for an extra $29.99 you can equip your JuiceBox with “Flexible J1772 Cable”  described as follows:

“Outfit your JuiceBox with a flexible & thin 40A 25FT non-UL J1772 (output) cable!

For those who value portability, or ease of cable manipulation, we are glad to offer a highly flexible and thin output cable option. With the addition of this option, your fully warrantied and assembled JuiceBox will come ready to go with a 25FT 40A portable spec output cable.
Please note that this cable is not UL rated, and not designed for compliance with national electrical standards. It is tested as safe to use for the power rating presented. Please note the cable you receive may not appear exactly as pictured – though dimensions and cable materials will be consistent.

So it may be that my original unit came with the “flexible” cable by default, but the new unit comes with a larger UL listed cable. (The cord I got on the replacement unit is shorter than my original by a good five to six feet.)


GFI cause update:

I have identified the cause of the GFI events (my TSM2500 chargers cause a GFI event when they shut down due to overheating.) The new charger still gets knocked “offline” when a GFI event happens, but it appears to recover on it’s own without needing me to power cycle it.


Pebble screen corruption issue (take 2… 3)

My original pebble watch suffered from the screen corruption issue that has apparently been plaguing all of the 301BL models.

Pebble was responsive and replaced it relatively quickly two months ago. Unfortunately, the replacement watch started to show the same types of issues, visible here in the region outside of the circle and around the first few digits on my Timer+ app.

I contacted pebble and after opening a case, sending them a photo of the watch’s serial number, etc, they sent me (another) replacement pebble and a prepaid label to return the previous replacement watch.
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Ring Video Doorbell Review

A few months ago I purchased a Ring video doorbell (along with a Chime Wifi announcer). This is a doorbell unit that has a video camera and motion detector built in, as well as the traditional button. It is powered either by your existing doorbell wires (if you have them) or via a rechargeable battery.

It requires a connection to your home Wifi access point to work, as well as a smartphone (iOS or Android) to be configured and make use of the “video” part of the video doorbell.

When somebody pushes the button, your smartphone gets a “video call” and you can see the person at the other end and talk with them (they can’t see you) from anywhere your smartphone has a network connection. It can also be set to send you an alert whenever the doorbell sees motion, even if nobody pushes the button.

If you have a wired doorbell already, and connect the ring unit up to your existing wires it also rings your existing hard-wired doorbell like a standard $5 button. If you buy the optional WiFi chime unit that plugs into a standard power outlet, it will ring that as well (just in case you don’t have your phone nearby while inside the house).

An optional added service is their “cloud recording” option, which costs $30 a year, and stores a video recording when it sees motion or the button is pressed. In my opinion, 90% of the “home security” value of the doorbell relies on this cloud recording option, so if you buy the ring video doorbell, plan on paying $30 a year (for each ring unit if you have multiple) as well. (Which is a lot cheaper than buying and installing your own video recording hardware.)

The benefits:

  • I really like being notified when motion occurs at my front door. It can tell you when packages are delivered (most delivery drivers push the button, but some do not and are detected by the motion detection feature), or when a family member arrives home.
  • The “video call” option can make it appear that somebody is inside the house, even when you are not. You can tell somebody that you are not interested, or to drop a package at the door, etc… (this can also be used to “greet” the visitor from within your own house without actually coming to the door, due to laziness or safety concerns.)
  • Having a doorbell with an obvious “video camera” built in should help with home security, as long as potential burglars notice it, even if it’s not working.
  • Having a video recording saved (offsite, in the cloud) every time there is motion near your front door is a very nice security feature. (This requires $30 a year subscription.) With this you can check to see if/when a package was delivered, even if you missed the initial “call” from the doorbell, as well as the obvious home security applications.

The downsides (areas for improvement):

    • Motion detection can be overly sensitive, and not sensitive enough at the same time. The Ring unit has “zones” where you can turn on or turn off motion detection, and adjust the “range” of the motion detection. However, it uses passive IR detectors, which mostly detect movement of a heat source. My front door faces a street (about 50 feet away) and heat from moving cars will set off the Ring unless I turn all of the zones off except the one directly in front of the unit. And then, it will only detect motion from people if they actually step onto my porch. Even so, very hot vehicles (such as garbage trucks) will still trigger a motion alert. My motion sensitive lights do a better job of detecting people walking around without getting false positives from the road.
      Ideally, you will be able to mount it such that a road is not in it’s field of view, even if the road is relatively far away from the front of the house.


  • The wifi/network connection is mostly fast enough, but not always. Typically I will get a notification on my cell phone within a few seconds of motion being detected or the button being pushed. However, sometimes this delay extends into the 10-30 second range, by which time whoever was there has already left. If you pay the $30 a year fee for “cloud recording”, you can go back and view who you missed, but you can’t actually talk with them. And on one memorable occasion when they were having problems with their servers, the Chime wifi doorbell announcer unit would “ring” about 10 minutes after the Ring doorbell was pushed!
  • If the doorbell isn’t connected to existing doorbell wires driven by a low voltage AC transformer, you need to take it off the wall and re-charge it every few months. The battery life is quite respectable, even with the motion detection settings set to “frequent” it lasted around 50 days for me and if you turn the motion detection settings to “smart” it should last 2-3 months. But still, it takes 5 minutes to find the special security screwdriver they include in the package, take it off the wall and plug it in. (Also, you don’t have a doorbell for the 8 hours it takes to charge.) The phone application will notify you when the battery is getting low.
  • It requires wifi to work. If your DSL goes down or wifi router is on the blink, your doorbell will not sound a chime. (Even though the Ring unit makes some noise and flashes a light when the button is pushed, giving the person outside the impression that the doorbell activated. (If you have it hard wired into a “real” doorbell it will at least ring the wired doorbel inside your house, even if it can’t notify your smartphone.)

Overall I’m happy with the device, and it works relatively well overall, but having it hard wired into a “real” doorbell would definitely improve things. I think that if you are replacing an existing (wired) doorbell button it would provide the best experience. Our house had a wired doorbell at one point in time (but it was replaced with a wireless doorbell before we moved in) so I’m hoping to re-wire the Ring unit up to a physical doorbell and low voltage AC transformer so that it will work as well as a regular doorbell even with networking glitches, and never need to be re-charged. The biggest win in my mind is having a cloud based recording of any motion near your front door.


Update 2016: After being installed for several years, I had an issue where the screws in the bottom of the ring got corroded, and “stuck” to the push in metal nuts inside the ring. when I tried to unscrew the doorbell to charge, the metal nuts broke free of the plastic. (This may be because the people who pressure washed the townhomes were were living in had used some type of chemical that wasn’t good for the metal.) The ring doorbell itself still worked, but it wouldn’t mount anymore. Ring customer support sent me a free replacement, which was very nice of them, as it was out of the 1 year warranty.

Update 2018: I came home one day to find my ring doorbell unresponsive. I thought it might be due to a low battery, so I charged it up, but it turns out that the problem was something else. Although it would accept a charge, we were unable to get it to “boot” up, or attach to a wifi network. Ring Technical Support walked me through the procedure to reset the unit to the factor default firmware/bootloader, but that did not work. Luckily for me, I had recently signed up for the Ring Protect Plus service, which includes extra warranties on the devices, so they sent me a replacement unit.  The screws on the bottom of this unit showed some small evidence of corrosion, but it was not as bad as the previous unit and they did not get stuck.

All in all, the ring devices appear to be relatively robust, the technical support is top notch, and if you are signed up for the Ring Protect Plus plan the warranty coverage is very good.

How I melted my ANOVA Precision cooker



I purchased an ANOVA precision cooker (a Sous-vide immersion heater) via their Kickstarter almost a year ago and have been having fun cooking things in water baths. (It makes cooking salmon so very easy….)

My wife told me about a recipe where you simmer a can of sweetened condensed milk in near boiling water for three hours to make Carmel. After my initial “But won’t it explode?” questions were answered (don’t use a pop top can and you are supposedly explosion safe…) I checked my ANOVA’s manual, and sure enough, it listed the Max temperature at 99 C, perfect for keeping water at a very low simmer without having to keep an eye on the range…[1].

Little did I know, the ANOVA can’t actually take being exposed to steaming water for 3 hours. Continue reading

Original Pebble Review + Application / Watchface Recommendations

I finally jumped on the “SmartWatch” bandwagon (after the CST – “World’s Thinest Watch” Kickstarter I’d been waiting on for two years finally gave up the ghost) purchasing a refurbished (Jet Black, original plastic) Pebble for $60 from

I can’t imagine paying $300+ for an Android Wear or apple Smartwatch when you can get the original Pebble’s new on ebay and discount websites for $50-$60. It does everything you really want a smart watch to do, at a fraction of the price.
Built in features I use and love:
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Lines appearing on the display of my Pebble

My original Pebble smart watch (purchased refurbished) started to have a problem where the display would get corrupted. It mostly only occurred when I was pushing a button to change the display, or when my stopwatch/timer was running (updating the display continuously). For day to day use of just wearing the watch, the screen would be normal much of the time.

I thought at first that something was just corrupted in software, so I removed all of my applications, but that didn’t fix it. Then I reset the watch, and that didn’t fix it. Then I rebooted the watch, and that didn’t fix it. Then I reset the watch to the factory default settings with a super hard reboot and reinstall (removing the custom firmware I had installed), and that didn’t fix it. So, I admitted that it was probably a hardware issue, and found this page on the pebble website that talked about “screen issues”.


I’ve found lots of information on the Internet that tells me this is a problem with the internal ribbon/zebra cable connector not staying connected properly.

I found this video that tells how to fix the ribbon/zebra cable connection issue by adding toilet paper in the back of the watch to hold it down.

If you don’t like opening your watch, and trust that it is actually water resistant, I also found this youtube video how to try and fix it by putting it into hot and cold water (but that doesn’t fix it permanently).

Luckily for me, I was apparently still within my 90 day refurbished watch guarantee, and Pebble is swapping out my watch for a replacement, so I don’t need to stuff toilet paper in the back of my watch. If you experience this type of issue you should report it to Pebble quickly. It appears to especially plague early Pebble / Pebble Steel watches, I presume they have changed their manufacturing process to keep it from happening to the later ones.