3D model description
A barrier to putting hydraulics on your e-bike is lack of availability for installing a switch on them, in order to cut out your e-assist, activate regenerative braking, or whatever else you might want to have happen when you pull the brakes. This adapter allows you to install an adjustable, weatherproof, switch on the brake lever of a Shimano BR-MT201 hydraulic disk system. It clamps firmly around the brake lever and switch components - you don't need to drill any holes in your brakes or apply any tape or glue. You can still access the fill-port on the reservoir, in fact the hole for it helps keep the sensor-holder snug and oriented.
This adapter is designed around the Shimano BR-MT201, which is a great value hydraulic disk brake set, and the Littlefuse 59025 series reed switch and associated 57025 magnet. Reed switches are completely encapsulated switches activated by proximity to a magnet. They have no (external) moving parts making them ideal for harsh, wet, environments. The 59025 series are medium-sized, available with normally-closed, normally-open, or changeover contacts, and can do up to 265 Vac/300 Vdc at 10 VA. You can get them from digikey (for example) for ~$14 including actuating magnet. The switch/activator get clamped in appropriately-sized grooves in the holders, so you can slide them back and forth to adjust the tripping point. In the attached photos I've got it set up to trip with a slight pull of the lever (before the brakes actually engage) using a "U" sensitivity-level switch.
You'll also need five #4x1/2" wood screws for joining the two halves of the adapter together (2 for the sensor holder, and 3 for the magnet holder). The screws come from the bottom, so you don't have to look at them when riding around.
If you look through the 59025 series datasheet you might select a different switch element, but if you're not sure I've got a good general case listed here. For each lever you'll need:
* The parts you print (either left or right)
* 5x #4x1/2" wood screws (flat head, countersunk)
* Littlefuse Part Number 59025-3-U-02-A (this is the changeover version, in case you're not sure if you need NO or NC for your setup, or just want to future-proof and don't mind the extra ~1g for a third wire)
* Littlefuse Part Number 57025
You probably also need to connect it to your control system with a connector of some kind... If you're using the cycle-analyst from Grin you'll want:
* JST part number SMR-04V-B
* 4 of JST part number SYM-001T-P0.6(N)
* some heatshrink tubing to finish it
3D printing settings
I designed this for FDM printing, but I think it should work fine in resin too. I like to orient the sensor holders end-on standing up on the build plate, and the magnet holders flat-side down for best results. I've had good luck printing them without supports, but you might want to turn them on for the hole in the sensor holder depending how well bridging works for you. I made the prototypes out of PLA, until I had the fit right, and they seemed to work well. But once I was happy with it I printed my "final" versions out of PETG +carbon, and that's the version I've been using now for months. They shouldn't really encounter any strong forces unless you crash.