Odds & Ends

The MVP Approach for Home Projects

Last year, for my daughter’s second birthday her father and I decided to give her a sand and water table. We had spent many hours watching her play with the sand and water table at the CuriOdyssey Museum at Coyote Point. Their beautiful table has two pans, each quite large. The upper one drains into the lower one which drains into a reservoir. The water in the reservoir is pushed through a UV water filter before it is pumped back to the top. Another awesome feature for their table is that the rate for pumping changes based on how much water is flowing into the reservoir. So if the children dam the water flow, then the pump slows to a trickle. If the water is flowing full force into the reservoir, then the pumping happens at full force.

We wanted to recreate this table for our water-loving child. We’re both engineers so we bought a 12V pump, a 12V UV filter, and found a 12V battery and charger. We happened to have a small solar panel from an earlier project. We needed a waterproof table with sides, adjustable legs to put the table at an angle, and a reservoir for the water. We managed to score a stainless steel sink from craigslist, but this was just 2 weeks before our daughter’s birthday party, so we clearly weren’t going to have time to build out the whole table in time.

So it was time to apply some of Mindtribe’s method and create a feature set for our minimum viable product (MVP). We clearly needed to cut some features that the table at CuriOddysey has. Flow control went first. We love the feature but our target market wouldn’t care. Regularly emptying out the water reservoir (into some potted plants) would also allow us to skip the UV filter. We scrounged up a 12V AC/DC power supply and wired that directly to the pump, thereby skipping the battery and solar panel.

Now we were ready for our first test run, our daughter’s birthday party. We placed our sink on some crates, added sand, and the party started.

Our minimum viable product was a huge success. The kids were having a terrific time, and we were discovering all the issues in our system. The children loved it, and it called for a more thought-out revision. First, we needed to prevent the sand from getting into the pump through the drain hole (pictured below). Our first solution was a cloth. sand-water-table-drain sand-water-table-cloth-screen The cloth worked but caused a water back-up. Next, we switched to a plastic screen. The plastic screen, however, was not UV rated. So we finally switched that to stainless steel, and now it matches the sink. sand-water-table-steel-screen Someday we’ll come up with a more impressive set of legs where we can adjust the angle and therefore the speed of water flow, but for now we’ll use the crates with a few bricks. sand-water-table-crates-1

We’ve also improved out water storage so it has a lid – ergo less likely to be a breeding ground for mosquitos – and our electronics now live inside a plastic box as well. And we’ve attached the battery, charger and solar panel. There’s still plenty of work to do, but if we had waited to get all the features into the first “release” (we have a UV filter for the water, for example but it is still uninstalled), our daughter wouldn’t have had the pleasure of her sand and water table these past 9 months. sand-water-table-crates-2