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When a Scooba user presses the Clean button, the Controller runs down a check-list to make certain that a group of movable / removable mechanical assemblies are in their operational positions. To assist the CPU in making those determinations, a corresponding group of magnetically actuated "reed"-switches are used throughout Scooba to monitor binary states of hardware items that an owner may cause to be in / out, or up / down relative to the robot.
Not everyone has encountered, i.e., physically seen a bare reed-switch, so, if you fall in that category it would be useful to visit this site to see what they look like. Scooba's switches are all mounted in some manner that obscures a good view of the glass-bodied switch. Locations of each known reed-switch and its actuating magnet are revealed in this section.
Owners should appreciate a robot that shuts off power to its motors when the operating robot is picked up from the floor. The robot may be spinning two or three mechanical items that project outward, thus presenting a physical threat to an operator's body parts. That shut-off function is triggered by a 'wheel-dropped, sensor system' provided for all wheels. This section looks only at the drive-wheel's reed-switch implementation.
Looking at the panorama duo in Figure 1, the left scene shows Scooba's LH-wheel assembly (the upper-chassis has been removed from the robot, so this view is from above, and looking a little rearward), and just forward, nearer to the viewer, a green-colored PWB is seen. The reed-SW is bonded to a slot cut though the PWB at, roughly, a central location. The switch can barely be resolved as a grayish rectangle.
Figure 1. Drive-Wheels Up/Down, Sensor-Switch
In that LH-view, the wheel is UP, since the robot is resting on a table. Notice the screw-head holding (white) parts of the drive-wheel assembly together. The screw can give us a location reference to the bar magnet that actuates that reed-SW. Now, view the RH-frame of Figure 1. That is the image of the wheel-housing after the drive-wheel and speed-reduction gears have been removed -- all necessary steps to view the bar-magnet's mounting hole. In that view, it is the upper left hole that our reference screw fits. Just below that screw-position, there is a cylindrical-post then another, larger, hole. That's the magnet's pocket. The actual magnet is shown here, in Fig. 2.
Now that you know where the magnet resides in the moving assembly, you can go back the LH-frame and visualize the magnet must be very close to the central zone of the little PWB when the wheel is UP, in its cleaning position; hence, the switch is magnetically actuated.
When a Scooba user presses the Clean button, the Controller must not start any motor until the Cleaning-Head has been confirmed 'latched'. If the Cleaning Head were to be left on the sink-top, and Scooba were to be allowed to operate without it, solution would be sprayed on the floor, but none of it would be collected!
Scooba is designed to avoid that Customer-Service nightmare by use of the reed-switch and magnet installations shown in Figure 2. In the RH-scene, the bar magnet is shown as a small, black rectangle located near bottom-center of the image showing the RH-end of the Cleaning Head. At left, we see another reed-switch mounting tactic (used here and one other place); not only is the switch and PWB assembly immersed in a tub of (clear) sealant, but the board is also retined by fusion-staking at two points. It seems likely that the board-assembly is staked into place, and later 'conformal coated to water-proof it. This is the assembly with two green wires connected to it; and there is a good view of the reed-SW bonded into the rectangular hole in the PWB material.
Figure 2. Cleaning-Head Latched, Sensor-Switch Components
Incidentally, also seen in that LH-scene of Figure 2, there is an oblique view of the RHS Wheel-Drop, reed-SW assembly. Almost an edge-view, this PWB is connected using two orange wires. The out-of-focus, black-blob at bottom-center is Scooba's left tire.
In the left half of Figure 3 we see a reed-switch mounting that is almost identical to that used for the Cleaning Head, except this one is way over at the robot's LHS, and is used to sense the adjacency of the bar-magnet which is carried in the Filter-screen's plastic frame -- as shown at right. Users may not notice that little black pellet while handling / cleaning the screen, since it is mounted on the underneath side of the assembly.
Figure 3. Filter-Screen's In / Out Sensor Components
In case anyone needs orientation for that LH-scene, the shot is taken just aft of plumb, the brush-motor can be seen at the very top of the frame, and its gear-housing is the white / whitish plastic at top-left / left. The LH-Wheel is just off scene to lower left.
Prior to starting Scooba on a cleaning mission, it is critical to performance that the Tank Assembly be properly latched down, and that condition is reported to the Controller by a reed-switch that is mounted on the Control Panel's PWB. Figure 4 flashes an image of that PWB but we can't see the reed-SW from this side (That PWB connects to the panel-switches with a stiff, etched-conductor cable. Stressing that cable by folding out the PWB just to take a shot of the reed-SW was deemed undesirable -- so we will have to get along with the following word-description.).
Figure 4. Tank-Latched Sensor
The metal, shield-can which surrounds the serial-connector is a great landmark for this description. Take into account that the PWB is inverted from its normal orientation when mounted on the robot, so its aft-edge is facing away from us. By looking at Fig.1 here, you will see the serial-connector at the right side of a rectangular block, which happens to be right below the reed-switch location. You then know that the position of the switch on the Control-Panel's PWB is about an inch to the left of the SCI-jack, and mounted fairly close to the PWB's aft-edge.
Talking about that "rectangular block", that item is a sprung-slider-block which assists Tank un-latching; however, the important relationship to notice here is the item on the Tank that it pushes against. See the RH-scene in Figure 4. That white-structure is bonded to the Tank. Its lower edge is the reaction surface for that sprung-slider; but at the upper end, you will see another one of those bar-magnets, and it is the one that actuates the reed-switch on the referent PWB.
One more thing, before leaving this Tank-Latched Sensor. Like all reed-switches, this one has a dynamic range of action which is dependent on the strength of the magnet, its air-gap to the reed-SW, orientation of the switch with respect to the magnet, and on magnetic characteristics of the specific reed-switch. That all says the switch will actuate at differing ranges to the magnet, in different Scoobas. The reason for emphasizing that state of affairs is it can be the cause of ineffective solution collection by Scooba IF the battery has not been inserted strictly in accordance with instructions in the Owner's-Manual. For more detail about that potential problem see the WARNING near the end of that page.
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This page is currently maintained by G. Plews