But once power started flowing, output voltage collapsed to 7.5V and remained there until a power cycle like the HP power supply did. I verified its open circuit voltage was over 19 V, connected it to a Neato, which again woke up thinking thereвЂ™s a charger. So I pulled out an old salvaged Dell power supply that only claims to deliver 19.5 V but could do so at 3.34 A. The Neato is very optimistic, showing itself to be charging, but there is negligible actual progress in charging the battery.Д«ut now that I know the current capacity is the limiting concern, maybe another power supply with higher amperage limits will work even if its maximum voltage is lower than 24 Volts. After collapse, it quickly builds up to about 15, then the voltage collapses again. Again its open circuit voltage is 24V as advertised, but once wired to a Neato, the voltage collapses to around 12. Does this also have an over-current protection mechanism? The real question is how it behaves when connected to something that draws more than its rated 1.7A. This is better than the unit inside a Neato, but now we know this is only part of the story. The second salvaged power supply had VeriFone branding and claimed it is capable of 24V 1.7A. Which explains the HP power supply behavior: it is an over-current protection mechanism that is great for safety in case of short circuits but inconvenient for trying to charge a Neato. But it does mean the Neato will happily soak up more than the rated power of its power supply. NiMH batteries are fairly durable so this isnвЂ™t necessarily a horrible thing to do in and of itself. Since thatвЂ™s within the range of NiMH battery voltage, it appears the Neato had connected its DC input directly into its batteries. My bench power supply immediately hit the current limit I had set, and voltage has sagged to a little over 14V. I set the dials to 24V and 1.67A, like the label on Neato charging dockвЂ™s power supply, and hooked up the wires. I then did what, in hindsight, I should have done as my first step: tried charging my vacuum with a bench power supply. This behavior indicated no permanent damage was done, but that I had tripped some sort of internal protection mechanism. I thought maybe I burned out something, but if I unplug the power supply and plug it back in, its output open circuit voltage was back up to 24V. The output voltage on the power supply had dropped to under 1V and remained there. The Neato woke up as if it saw a power source, but two seconds later it acted as if the power source went away. First I verified the open circuit voltage was 24V, then I clipped it to the vacuum.

The HP power supply label said 24V 1.5A, which is slightly lower than 24V 1.67A listed on the supply inside a Neato dock, but I thought it was worth a try. The first candidate was a power supply with HP branding. Since I didnвЂ™t have a good way to make contact with a NeatoвЂ™s charging strips, I opened up my robot vacuum and rigged up a test configuration using clip leads on my crowded workbench. I bought two 24V DC power supplies similar to that inside a Neato charging dock at the W6TRW swap meet. Hers had the advantage of a charging dock so we could open one up to see how it worked.ДЄrmed with that knowledge, I thought IвЂ™d try to build my own replacement charging dock for my Neato XV-21. I made enough progress to catch вЂ™s interest, who saw another Neato robot vacuum in a thrift store and bought it. I originally thought I would buy it just for parts but itвЂ™s been a long and interesting adventure poking at how these robot vacuums worked. It got under six-inch obstacles, edged its way into tight spaces, and seamlessly transitioned from low carpets to solid floors.When I found my Neato XV-21 in a thrift store, it wouldnвЂ™t power on and it didnвЂ™t have its charging dock. Unobstructed, the Neato proved it had powerful suction and the ability to seek out dirt and pet hair. But where Neato can't reach, it can't eat. Like a stingray, the Neato XV-21 weaves its way across the ground, eating up dirt as it goes. It's sort of a cross between the 'visual' camera-based mapping used by Miele and Samsung, and the real-time infrared detection used by iRobot. Neato vacuums have infrared sensors that map out a room before heading out to clean.

The only thing you have to do is empty the 28-gram bin about twice a week. The Neato XV-21 can be programmed to run once a day at a different time each day. What a robot vacuum can do is work while you're away. You see, a robot vacuum can't clean as well as a human being with an upright. Before you let the XV-21 loose, you need to define a schedule. Now that you've charged up your Neato and set up the magnetic boundaries, ready to start cleaning? No, you're not. Those big wheels help the Neato XV-21 cross thresholds.

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