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Dirty air filters waste energy and stop trapping dust as they get clogged. FilterWatch will alert you when your filter needs changing.

We started a blog that you can get to here. Get some more insights to what we are thinking and leave us your thoughts as well.

When we created this air flow sensor, we had one thing in mind, the money flying out the window whenever we forgot to change our HVAC air filters. That is just the tip of the iceberg. We are not going to be able to do it all, let alone think of all the ideas possible, so we decided to create a reward for just the air speed sensor. You provide power and ground. We want it to work for you right out of the box so the analog outputs you get will be proportional to air temperature and air speed. All other command and control can be done serially (including getting air speed and air temperature data). Everything you need to create your own long term, low power monitor of air flow.

Not a low level DIYer?. No problem, we are focused on long term monitoring of your HVAC air filter. One of the biggest energy wasters and also a cause of numerous respiratory issues are dirty HVAC air filters.

Read below for some valuable information regarding respiratory problems associated with dirty air filters and please consider supporting the effort.

Plain and simple, FilterWatch is here to relieve you from having to remember to change the air-filters in your home. As your air filters get dirtier and dirtier, they get less and less effective at doing what they are supposed to do, clean your indoor air. To add insult injury, they are costing you a lot of extra money in wasted energy.

Indoor dust, mites, pollen, and dander are major triggers of asthma and other respiratory aliments. One of the best methods of limiting these allergens in your home, is to trap them in your HVAC filter.  As your air filters get clogged with these allergens, they become less and less effective. Lower air flow through the filter and poor seating due to flexing of the filter are just a couple reasons they become less effective at trapping particles.

Are your HEPA filters protecting your family? They might be for a while, but they get clogged as well and their effectiveness is quickly reduced as the airflow is reduced by clogging.

FilterWatch is not just a simple timer though, FilterWatch is a very precise sensor that monitors the air-flow going into your HVAC system. It then makes an intelligent decision as to when it is time to change the filter based on a reduction in air-flow. This reduction occurs as your filter gets dirty.

Clean air filters mean cleaner air in your house. As filters get clogged, more dust particles eventually find there way through the filter and back into your house.  

Check out what that looks like in my house:

Dust escapes through a clogged filter and around the rim as it bends.
Dust escapes through a clogged filter and around the rim as it bends.

FilterWatch will tell you to change your filter when it is ready to be changed based on how dirty it is.  During the high use season it might be 15 days, we can't say for sure. 

What we can say is that the condition of your filter directly affects its ability to clean the air in your home AND that your HVAC filter is one of your best defenses against airborne contaminants. Check out the information at the following link. It summarizes several studies related to the effectiveness of different filters, whole home filtration, and room filtration all related to controlling indoor allergens. If you or your family are affected by respiratory ailments such as asthma please read THIS SUMMARY OF SEVERAL STUDIES!

The Department of Energy states that maintaining a clean air filter will reduce your HVAC energy consumption by as much as 5-15%.

Why is it that many people forget to change the air filters in their house if they are able to save that kind of money by doing so? It can be a nasty chore. Bump it on the way out and all the dust collected is on the floor or your head. The less often you change it, the less often you have to deal with it. I can think of a hundred things I'd rather do and that helps me forget!

Dirty air filters are the single biggest cause of wasted energy in most homes and wasted energy means wasted money!

It's all about getting as much of the hot or cold air as your system can generate into the house as fast as possible so the system can turn off.

A clean filter with proper sealing and insulation in your home will get you the maximum benefit from your HVAC system.

When is the RIGHT TIME to change your air filters?

Some people like to change their air filters every 30 days and why wouldn't you when the label on the air filter says "30 day filter"?

Some people like to look through the return vent to see if the filter is dirty or 'bending'.

What if your air  filter is already 30% clogged after 30 days or when you look at it? Worse yet, what if you forget to check your filter for a couple extra weeks and it's even worse?

Saving Energy = Saving Money

The Department of Energy states on their website that maintaining a clean air filter will reduce your HVAC energy consumption by as much as 5-15%.

This link will take you to a study by Old Dominion University that shows the added cost of electricity each month given a 23% clogged air filter. It's over $13 per month with just 5 hrs of running per day at $.1 per kWh! A 20% increase over the cost of running with a clean air filter. 

Old Dominion Study

Check out a related chart with ESTIMATED EXTRA ENERGY COSTS based on the clogged % of an HVAC air filter. These numbers match up pretty close to the Old Dominion study as well as the Department of Energy's 5-15%.

Still not convinced? Just read the first few lines of this study funded by the Department of Energy back in 2003. "The most common problems affecting residential and light commercial heating, ventilation, and air-conditioning (HVAC) systems are slow refrigerant leaks and dirty air filters".

DOE Funded Study

It's all about getting as much of the hot or cold air as your system can generate into the house as fast as possible so the system can turn off.

Of course, you need to also make sure your house is holding the conditioned air sufficiently with proper sealing and insulation to get the maximum benefit from your HVAC system.

How does FilterWatch operate?

FilterWatch comes with a small mounting bracket that gets attached to the rim of the return vent (near the filter) or a room vent. A reset button is used to tell the monitor that a new filter has been installed. Snap FilterWatch to the mounting bracket and from this point on there is nothing to do. An LED and a BEEPER will tell you when the filter needs to be changed.

When FilterWatch measures an air flow change around 20% lower than the initial reading, the alarm will go off about once every minute until the user resets the sensor or changes the air filter. Of course, a wireless version will give the user the ability to SET the desired % that generates an alarm.

Who needs FilterWatch?

If you are forgetful  about checking your air filter(s), You need FilterWatch.

When you can see the dust buildup on the vents, or your air filter is half sucked up into the ducting, it's way past time to change the filter! You need FilterWatch.

If you are pretty good about changing your filter every 30 days but you have a couple extra people and pets in the household. You need FilterWatch.

Is your return vent near the ground next to a utility room where the dogs and kids run in and out of the house?

Does Fido sleep next to the return vent?

Do you live in a dusty region?

Do you use a HEPA filter that catches more airborne contaminants?

These are all environmental issues that can lead to your air filter being clogged earlier than you would suspect.


How far along are we?

We've built several FilterWatch monitors to work out issues with different readings based on part variance and manufacturing variance.

Checking monitors against another anemometer.
Checking monitors against another anemometer.

A SINGLE AA battery is all that is needed to power the device for over 1 year. A signal will occur when the battery needs replacing. 

We've also tested FilterWatch with smart HVAC systems that have variable speed motors.

Our next big step will be packaging, we know roughly what shape we want, how we want the battery installed, and where the LCD display (anemometer option), button, and LED are located and you can see that below in a simple 2D drawing below.

Proposed Layout
Proposed Layout

With the funds we hope to gather here we will have the package professionally designed and put into molds. 

What's this about an anemometer?

In developing the software for FilterWatch, we had to develop an air speed sensing capability to test the device. That's the only real reason we added an LCD as well. With added software, an LCD and little more electronics, FilterWatch can also function as a neat little anemometer targeted at consistent lower speed air flow. (non-gusting, 0-25mph-ish).     It's perfect for the user that wants to manually check the wind speed coming out of many registers or into return vents and even many windy conditions outside.


Our plan is to manufacture and assemble the PCBs locally. We have plenty of local manufacturing contacts that we have used in the past.

We have already visited local injection molding companies to get budget pricing on a 4 piece mold with multiple cavities to allow for different colors.

We plan on internally setting up a semi-automated calibration/test station to program the final calibration tables into each device.


Between now and the end of the fund raise we will have made another PCB which captures all of the changes to date and makes the whole unit approximately 75mm (3") long and only 19mm  (.75")  tall and about 25mm (1") wide.

End of AUG: Plastic package design done

End of Sept: First molded parts and first assembled PCBs for validation

End of Oct: First fully assembled PCB, and plastic parts start arriving for final assembly and test.

Mid Nov: Final Assembly and Test complete

3rd wk Nov: Product start shipping

What are the funds used for?

  • 3D package design (~5k)
  • Mold(s) (~12k)
  • Small initial build to validate manufacturing (~2K)
  • Volume purchase for awards ~(9K per qty 1000)

The Team

Mike Mayer - SIma Engineering

John Pollock - Innovation Play

Between myself and Mike (see below), we have about 40 years of electronics and firmware development. We have both delivered products and have been successful. It's all because we don't compromise on performance and we listen to our customers.

Mike testing multiple units
Mike testing multiple units

Risks and challenges Learn about accountability on Kickstarter

We have tried to add a little extra time in the schedule to make up for technical slips along the way. Getting the injection molding right is always the biggest schedule risk for us because we depend on contract resources. We will 3D print the first designs to minimize re-work on molds which can impact the schedule.

We obviously cant test the device in every possible situation. There will be some instances where the device and mounting bracket do not attach easily to a vent. We anticipate making a few different mounting brackets to give FilterWatch access to the highest airflow into or out of a vent.

FilterWatch currently expects a minimum starting airflow of around 2 mph.


  • If you are an early backer at either $25 or $30. That is a wireless version BUT I will contact you when we are successful to see if you are happy with the BASIC version which will ship earlier. The basic version will also have an output connector for those who might want to connect the basic version in a wired fashion to a home controller.

    EARLY BACKERS - you get your choice.

    The $30 FilterWatch BASIC is for those who want a BASIC version as all the other rewards are taken.

    The $50 FILTERWATCH WIRELESS and FILTERWATCH with ANEMOMETER will get you the same ALL-IN version that includes EVERYTHING, wireless, anemometer.

    We added time to get the wireless implemented.

    Sorry for all the confusion.

    Last updated:
  • The way to order multiples is to over pledge at the level of reward you got in at and we will contact you to see if you were being generous or wanting a second unit. Many people have multiple HVAC units.

    We still have a long way to go and we thank you for the support.

    Last updated:
pledged of $32,000 goal
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  • Pledge $15 or more
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    3 backers

    SENSOR ONLY: This is for our Arduino and other DIYers. This a a sensor only board. You provide the power and we provide analog outputs proportional to air speed and temperature as well as serial connectivity for cmd/ctrl. Everything you need to create your own long term air speed monitor or other top secret project!

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  • Pledge $25 or more
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    100 backers All gone!

    KICKSTART US: You were one of the very first supporters and we are rewarding you with a FILTERWATCH at the lowest cost. This ships free to US addresses.

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  • Pledge $25 or more
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    8 backers

    FILTERWATCH BASIC: For those of youwho just want a really smart signal to know when its time change your air filter. This is the reward for you. It has the same intelligence when deciding how clogged your filter is BUT we use an LED and BEEPER to alert you. This version does include a port for those who might want to hook up a wired home automation system. This version ships out earlier than the MAX version.

    Estimated delivery:
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  • Pledge $30 or more
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    93 backers All gone!

    EARLY BIRD SPECIAL: Your and early bird and we thank you for the support, you get FilterWatch at an unbelievable cost. This ships free to US addresses.

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  • Pledge $50 or more
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    4 backers

    FILTERWATCH MAX (Bluetooth 4.0): If you want to connect FilterWatch directly to your mobile device using Bluetooth 4.0, this is the reward for you. We will support iOS and Android devices with a basic control and notification app.

    Estimated delivery:
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    8 backers All gone!

    FILTERWATCH with ANEMOMETER option: Look them up on AMAZON or EBAY and you'll see that an anemometer with no moving parts (hot wire) will set you back over $200. The anemometer we show in one of the images costs $79 and comes with the 'click' when the vane is spinning!?!?! Our anemometer won't have all the bells and whistles but you can count on it being precise and reliable. Use FilterWatch for 5 months during your high HVAC usage season and you'll probably save the cost of the device off your energy bill. Shipping is free to US addresses.

    Estimated delivery:
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  • Pledge $50 or more
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    33 backers

    FILTERWATCH MAX (ZigBee): This unit has it all. Wireless support if you want to communicate to your Smartthings controller or your WigWag controller. We included the anemometer option which adds the LCD and we included a port for wired installations.

    Estimated delivery:
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  • Pledge $50 or more
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    7 backers All gone!

    FILTERWATCH WIRELESS (ZigBee): If you want to connect FilterWatch to your Smartthings controller or any controller that supports the ZigBee Home Automation profile. This is the reward for you. PLEASE NOTE the added delivery time!

    Estimated delivery:
    Add $10 USD to ship outside the US
Funding period

- (50 days)