Clearblue easy sells a well-reviewed ovulation prediction kit (OPK) that essentially reads an ovulation strip and digitally tells the user whether or not she is in her fertile window. At $30-$40 for a pack of 20 tests ($25-$35 for a pack of 7 tests), they aren't the cheapest option out there.

Included in each box is a digital test reader, and sealed test sticks. You open and insert a test stick into the reader each day and test your urine, and then wait for the digital read out that comes in the form a smiley face or an empty circle.

On our first pack, we got a smiley face on the second day! I thought we could use it again next month with the same tester and the other 18 test sticks, but everything I read online seemed to say we'd have to buy a new pack. Anyways, I cracked open the digital test reader, and found a couple of batteries, and a microchip controller (Holtek HT48C06, http://www.holtek.com/english/docum/uc/48x050608_1.htm). I didn't want the results from last month to affect the reader this month, so I popped out the batteries and put them back in to hopefully reset any counter or memory in the reader.

I also bought another pack for this month so I'd have two testers (one new and one reset) to make sure everything is working as it should. And we got two smiley faces on Day 14! A couple caveats: I don't know that removing the battery actually resets anything. It could be that you could just keep using the tester and it would work just fine. A better experiment might be to have one tester that has been reset, one new tester, and one tester that has not been reset to then see how each performs, but at $30/box and ~$1 per test stick, it's an expensive experiment I'm not going to be doing any time soon. If any readers do try this out, let us know in the comments! Alternatively, if you can make sense of the technical document for the Holtek chip, likewise, we'd love to know!

Final note: while Clearblue does not sell refill packs of the test sticks, the test sticks for the Fertility Monitor seem to fit inside the OPK testers. This month we've just been using the test sticks from the OPK boxes, and if we go again next month, I'll be giving the fertility monitor test sticks a try. The Fertility Monitor Test sticks come in boxes of 30, and are about $30-$40 from Amazon.

Step 1: Open tester

On the side above the display, there is a notch you can use to open the tester. I use a quarter, which fits in nicely, or you can use a spudger (if you have one). Pry the tester open, and pull apart. The top should snap off.
<p>My tester only has one battery, same brand, but when I tried this it gave me a &quot;read FAQ instructions&quot; Icon (little open book with arrow)</p>
Maybe they updated the product?
<p>no need for clearblue test... just make love everyday ! it works great !</p>
awesome idea!
You bought it so it is yours to make with it whatever you want. <br>And since we have freedom of speech, noone can forbid you to spread the word. <br>
Yup, never signed any EULA!
An EULA is also not everywhere binding... If you life in europe, EULA's arent legal contracts and in no way binding. Sign any EULA you want. They have squat on you... <br>Especially if you have to open (and thus void the return-right) the package (Or even worse: If you have to install the Software) to read the EULA... <br>Buying a cat in a bag? Not in europe, pal... :)
Careful... the folks at Unilever (or whichever consumer medical product corporation markets Clearblue) may not take kindly to such a consumer-friendly and useful adaptation of their products. This is brilliant, and hopefully it saves a lot of people a lot of money.
Thanks for the comment! I hope people find it useful.
Im not sure there is too much they can do if someone simply spread the word of this. The instructable might be able to be traced but i doubt they'd bother. <br> <br>Great idea! Saves a lot of money!

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