ERV/HRV Ventilator Setup, Balancing, and Micro-balancing

1. ERV/HRV Balancing Background and Overview

I decided to write this guide after reading through the Honeywell install manual for a ERV and HRV I installed and being very dissatisfied with the ventilator balancing instructions.  I figured there must be others out there wanting some clarity on how to balance a ERV/HRV properly. Balancing a ventilation system is something normally left for the pros, but an extreme DIY’er can do it if they have a good understanding of the whole system.  It is possible to balance your ERV or HRV without any special tools like a manometer or magnehelic differential pressure gauge if absolutely needed, which I will explain below, but still best to have some measurement devices.  A word of caution, this is something you don’t want to mess up, proper balanced ventilation is absolutely essential in certain climates. In the north, where vapor barriers are used, if the house is under positive pressure you will be pushing moist air into the wall cavities in the winter where it can condensate.  But regardless of the climate it is still important to have a balanced system.  If you have any doubt get a pro in to do it.  I will not dive too much into how to install a whole house ventilator as it is outside the scope of this article and something best left to a pro if you are unsure of how to do it.

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Extech Formaldehyde (CH2O and HCHO) Meter Review


I started diving into research about Formaldehyde and how to measure it after my parents started having indoor air quality issues in a house they recently bought and remodeled.  I wanted to get some quantifiable metrics on what I could so I purchased a formaldehyde meter and sent off some air samples to a lab for testing.  I know this is only a small piece of a much larger picture in terms of indoor air quality (IAQ) but it seems to be an important part of the VOC side of IAQ.

The meter I ended up purchasing is the Extech Instruments FM200 Formaldehyde (CH2O or HCHO) Meter, I have had good experiences with Extech equipment in the past but as you will find in this review I was severely disappointed this time.

Extech FM200
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DIY Metal Halide Sunlight Simulator Light Therapy Light, Full Spectrum

1. Light Therapy Overview & Introduction

Sunlight simulation and light therapy light boxes are commonly used as light therapy for treatment of Seasonal Affective Disorder (SAD).  My mom has SAD and after seeing her wimpy light box I thought there had to be something better out there, after some research I was really surprised at the underwhelming sunlight simulator light therapy options on the market.  When I started this project my parents lived in the Northern Virginia \ DC area of USA where there are many overcast days in the winter months.  I love bright work lighting and lighting in general so part of me was happy that was not there was not a good option available on the market so I could be creative and make my own for her.  Most light therapy boxes use fluorescent lighting which I have never liked due to its spikes in a few bands on the spectral power distribution (spectral distribution or emission spectra, discussed below).  I love the full spectrum light of incandescent and halogens but to get a light bright enough to work for light therapy I needed a bulb in the 1100 watt halogen or 1500 watt incandescent range at minimum (likely much higher for ideal lumens) which is impractical in its power consumption and heat output.  The best all around option is a high intensity discharge (HID) light such as a ceramic metal halide which have some of the best Color Rendering Index (CRI), spectral distribution, lifespan, and cost of any non-incandescent light source.

When picking which light source to use for a light therapy box build it is worth noting the other options other than fluorescents and why I did not choose to use them.  First LEDs; the LED market is changing so quickly that whatever I say about the current LED options here will shortly be obsolete. When I started this project in 2013, high end, high power LEDs with very good spectral distribution were exponentially more expensive per lumen.  To build or buy a high quality LED lamp that outputs 15,000+ lumens would use multiple extremely expensive high power high CRI LED modules and would actually be less efficient lumen output per watt than ceramic metal halide in 2013. This is changing quickly and with time LEDs will overtake ceramic metal halide as the go-to choice.  The second option was arc lamps like xenon arc or similar.  While this is a very appealing lamp in terms of its emission spectral distribution characteristic (just about the best it gets and why they are commonly used in video projectors), metal halides are better from a practical and value standpoint.  Xenons arc lamps have short bulb lifes (about the same as an incandescent), are very expensive compared to metal halide, output large amounts of UV, have relatively low luminous efficacy (~40lm\w), and ballast are much harder to find and are more expensive.  If money was no object and heat was not an issue a well engineered xenon arc lamp would be the best option.

Metal halides are rarely seen in residential \ consumer lighting mainly due to their long startup times and higher prices but are the logical choice for sunlight simulation when startup times are not critical and will be turned on for long periods of time.  Ceramic metal halide lamps are superior over traditional quartz metal halides due to their higher CRI and luminous efficacy which is obtainable from higher internal temperatures.  When picking a metal halide bulb for a DIY lighting project there are some important things to keep in mind.  Most bulbs are not rated for open enclosures and need some form of protection from a bulb blowout.  This and all the bulbs specifications are listed in the bulb  choices section.  To give some background on what all the terminology is in the bulb comparison table, I have discussed a few keys points in the below section.

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Nexus 7 (Original 2012 version) Screen Flicker Fix

I bought the original Nexus 7 the day it came out in 2012 and since it has had an annoying screen flicker issue which is most visible on white backgrounds like surfing the web.   I have put up with this for over a year but finally got annoyed enough to see if there was a way to fix it.  I searched the web but did not find a solution to this issue.  I tried a bunch of stuff like tweaking Wi-Fi settings, setting the backlight to a constant brightness, and using root only backlight control program all will no luck.  It seems to be an EMI issue that stems from the Wi-Fi connection, if I turn off Wi-Fi the issue resolved itself but that makes the tablet pretty useless for my needs.  So I popped the back cover to see if I could shield the board from the Wi-Fi antenna.  I have been able to resolve the issue and here is a basic rundown of how to fix the issue.

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DIY Pipe Lamp with Eletrical Outlet and USB Charger

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I have always liked industrial architectural style and have wanted to make a pipe lamp out of black iron pipe for sometime.  I made this pipr lamp to go on a bedside table or dresser with a dimmer and USB port to charge devices.
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AVR & Nintendo DS to FTDI Vinculum USB Host HDR PTP/MTP Camera controller

I have created code and an interface that allows an Atmel AVR or Nintendo DS to control a DSLR camera through a FTDI Vinculum USB host controller.  The code implements a very basic subset of the Picture Transfer Protocol (PTP) / Picture Transfer Protocol (MTP) protocols which are used on DSLRs and many point and shoot cameras.  This interface allows an Atmel AVR or Nintendo DS to control a modern USB camera such as a DSLR.  I wanted to do this to create a standalone HDR controller without the need to haul around a laptop.  For more background information on why I decided to do this and the CPLD interface I created to allow a Nintendo DS to talk to the FTDI Vinculum please read my previous blog post.  I got the Nintendo DS / AVR USB controller working  in June and have not changed the code since August so it is long overdue for me to post the code and schematic.

The code was written and developed on an Atmel AVR (non-Arduino) and ported over to the DS.  It is much easier to develop code on an AVR then on the DS which you have to constantly swap SD cards on every recompile. I wrote the code to be as platform independent as I could so it can be moved to whichever device needed.  I do not think it would be too hard to add to the Open Camera Control Project (OCC) (talked about in last blog post) code, you will need to call a few functions to init the Vinculum and to take picture, change exposure time, etc.

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Nintendo DS Slot-2 (GBA) DMA to FTDI PFIFO Interface

In May of this year (2010) I wanted to create a USB HDR camera controller allowing me to shoot more then three bracketed shots quickly and in one set (most DSLRs only allow you to bracket up to three photos in one set).  There is a open source project already out there  to do this, the Open Camera Controller (OCC), this project uses a Nintendo DS or Nintendo DS Lite and a simple arduino interface cartridge to fire the remote shutter release on your camera.  This project has a really nice software interface, the only limitation is that most camera do not allow faster then 1/20 sec remote shutter release exposure times in bulb mode.  You also have to account for the frames per second rating of the camera and memory card speed.  So I wanted to switch to PTP/MTP USB control of the camera which can use the camera to the full extent of it’s capabilities but is much more complicated to implement.  I figured the best way to do this would be to try and add USB host capabilities to the Nintendo DS through an expansion card which would allow the possibly of adding USB control to the OCC project.

The first step was to figure out how the Nintendo DS (NDS) talks to the Slot-2 Game Boy Advanced (GBA) cartridge slot.  In the OCC project the NDS talks to the arduino by toggling one data line (pin-3 WR#) on the GBA SLOT-2 that is used to fire off the rumble motor in a rumble cartridge.  This allows the NDS to tell the OCC arduino to start and stop capture but will not work for the more complex data communication needed for USB control.  I started by learning how to compile code to run on the DS, then figuring out the code needed to talk to the GBA slot, reversed engineered the DMA the NDS uses to talk to the GBA slot, and finally wrote logic for a CPLD to convert the GBA SLOT-2 DMA interface into FTDI PFIFO interface used on the FTDI vinculum USB host controller.

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Luke's past and current projects…