Dettol / Sacrotan Soap Saver (Modified Gear)

thingiverse

Hey there! Hand washing is super important these days, and those automatic soap dispensers from Dettol, Sacrotan, or Cillit Bang can be pretty handy, but they often give out way too much soap, making you buy refills more often than necessary. Think about it, these companies make a profit by selling you the dispenser at cost price and then charging you for the refills. It's kind of like how printers charge you for their cartridges or automatic home deodorants do. In times when shopping can be a real challenge due to scarcity, saving soap is crucial to keep your hands clean frequently. So, here's what you need: a Dremel, soldering iron, sandpaper, grease lube, and a cutter. If you're using an FDM or FFF printer, print the two parts with the hub facing up, using supports. Make sure the side with the eccentric hub is smooth, without any support marks. For SLA or DLP printers, print the whole two-piece set in one go with the hub facing up at 45 degrees (check out the picture). Use "Blu" resin from Siraya Tech for a strong and precise finish. Again, make sure the face with the eccentric hub is smooth, without any support marks. To open your dispenser, remove the batteries and three screws, then insert a blade between the two upper parts near the soap output and LED assembly. Remove the internal plastic housing, inspect the wires and soap tube, and take out the external housing. Desolder the three wires, remove the pump assembly, and take out the four screws of the pump. Now, modify the pump to remove the intermediate panel (a red/yellow rectangle as shown in the photo). Leave enough plastic to keep the micro switch intact, cutting the panel at 45 degrees following the purple profile on the picture. Sandpaper should smooth out any support marks on the cam. Redrill the shaft with a Dremel so you can easily insert the original small shaft. Before reassembling, disassemble the cylinder part and clean it thoroughly (remove all soap residue). Grease the piston with Vaseline or standard grease, then clean the lens in front of the LED. Reinsert the piston-cylinder assembly, put in the new gear, and check that it rotates properly. If you hold the assembly facing you, with the new gear on the left and the switch on the right, the gear should turn counter-clockwise. The cam should push the switch blade correctly, and the piston should move up and down correctly. Put back the last long original gear (between the new gear and the motor), apply grease everywhere, and close the housing. Test the assembly with a small 4.5V power supply. Place the LED in front of the receiver (window) and remove it briefly, then put it back in place. The pump should only work once. If the pump works twice or more, there's a problem between the gear and cam junction. You might need to use "Assemblage 2mm Solid State," which has the gear and cam as one piece with a stronger shaft instead of a junction. In this case, remove all plastic from the housing to enlarge the space. I had issues on eight modified devices when trying it with the power supply. The resin part wasn't strong enough, and the gear axis broke, causing two or three doses of soap instead of one. Reassembly is easy: put back the pump unit, solder the wires, reposition the small switch and its plastic cover, reinsert the external box, replace the wires and LED correctly, screw the screws back in as shown in the picture using gravity. I hope you're happy with this modification, and your hands will stay clean for a much longer time.