Safety - The-Hybrid-Atelier/RheoBoard GitHub Wiki
Read this before connecting power, soldering, or running a pump. It covers RheoBoardOTS - DIY, RheoBoard_v1 - PCB, and RheoBoardPipette - Portable. RheoBoard is for teaching and research laboratories, not a medical or safety-critical device.
Marks
These are warning labels for this build. The sentence is how to read the mark.
| Mark | What it means |
|---|---|
| Shock. The 12 V adapter plugs into the wall. Unplug it before you wire. Do not feed 12 V into the ESP32. | |
| 5 V pin. Pump and valve current stays off the ESP32 5 V pin. | |
| Battery. One protected lithium cell, for the ESP32 only. 4.2 V at full charge. | |
| Burn. The soldering iron can burn you. Unplug power before you solder. | |
| Eyes. These builds make pressure and vacuum. Keep tubing, the nozzle, and open ports away from your eyes. | |
| Rest. Give each pump at least as much time off as time on. Unplug 12 V to stop the pumps and the valve. |
12 V adapter
The pumps and the valve run from a mains-powered 12 V DC adapter. On the DIY panel, USB powers the ESP32, and these assembly steps leave the battery disconnected. On the portable build, the battery powers the ESP32 only. A damaged mains cord, or a loose connection at the wall, can shock you.
Use a regulated, center-positive 12 V adapter with a barrel plug 5.5 mm outside and 2.5 mm inside.
- On the DIY panel, use at least 2 A. The adapter on Parts to buy is the Cysljoyful ALT-1202, 12 V at 2 A. Its barrel plug goes into the SparkFun PRT-10288 female jack. That jack is 5.5×2.1 mm. The ALT-1202 plug is 5.5 mm outside and 2.5 mm inside. Whether that plug fits that jack is unconfirmed. Confirm this plug-to-jack fit before proceeding to power-on. From the PRT-10288 screw terminals, a breadboard feeds both L298N motor-power inputs. The outer sleeve is negative and goes into the common ground, including both L298N GND screws and the ESP32 GND pin. The adapter does not power the ESP32.
- On the PCB, that plug fits the board's 12 V jack. The input fuse is 2 A. Start with a 12 V, 2 A adapter. A larger adapter does not increase the current the board is allowed to draw. The board makes about 4.5 V for the pumps and about 6 V for the valve.
Leave micro-USB, the battery, and the 12 V adapter disconnected while you connect electronics or tubing. Keep 12 V on the adapter input. Do not feed 12 V into the ESP32.
- On the DIY panel, leave the adapter unplugged from the wall while you wire, while you check continuity, and during upload and the controller-only startup in the RheoBoardOTS - DIY startup check. Power the ESP32 from micro-USB for those steps. The powered check in Step 05 applies 12 V only after the ALT-1202 plug-to-PRT-10288 jack fit is confirmed. The 12 V adapter feeds both L298N motor inputs directly, with no extra converters. The pumps are rated about 4.5 V and the valve about 6 V. This direct drive has been operated, including short REPs and continuous pumping. Whether that stays inside those ratings is still an open engineering question. Unplug the adapter from the wall if a pump or the valve moves while it should be idle, or if you see excess current or heat.
- On the PCB, apply 12 V the first time with the controller and the loads disconnected. Stop if the supply current-limits, a rail voltage is unexpected, or anything heats up. That check is in ASSEMBLY_AND_BRINGUP.md.
To stop the pumps and the valve, unplug the 12 V adapter from the wall. On the DIY panel, a double-click latches the vacuum pump in the sketch, so closing the app leaves it running. Double-click again to release it. On the PCB, a dropped controller link leaves the last command running, and the buttons do not cut 12 V.
ESP32 5 V pin
Keep pump and valve current off the ESP32 5 V pin.
On the DIY panel, the +5 V pin on each L298N is that module's own regulator. Motor power is the module's 12 V input. Leave each 5V-EN jumper on. With the jumper on, do not feed another 5 V supply into that pin, and do not tie the two modules' +5 V pins together. On the PCB, the pump and valve rails come from the board.
Battery
Portable power for the ESP32 is the SparkFun Lithium Ion Battery 1500 mAh, IEC62133 certified (PRT-26059) in the Thing Plus JST battery socket. It is one protected cell, 3.7 V nominal and 4.2 V at full charge. This pack powers the ESP32 only.
Use that socket for this pack, or for another single protected cell that stays at or below 4.2 V. Do not short the plug. If the pack is hot, swollen, or damaged, unplug it and stop using it.
Soldering
The iron can burn you. Unplug USB, the battery, and the 12 V adapter before you solder.
On the DIY panel, solder only when a header or a wire lead is not already fitted. On the PCB, the connectors, headers, and pumps are soldered on by hand.
Air
These builds produce pressure and vacuum. Keep tubing, the nozzle, and open pump ports away from your eyes. Keep the pressure modest.
Pumps and valve
The pumps are rated about 4.5 V. The valve is rated about 6 V. Drive them through the L298N on the DIY panel, or from the board rails on the PCB. On the DIY panel, 12 V goes to the L298N motor inputs, as stated above. Do not connect a pump or the valve straight across the 12 V adapter.
Adafruit's about 50% duty-cycle note means time on and time off. Give each pump at least as much rest as run time. A REP may use a short higher-PWM pulse. A latched vacuum, or the serial commands PUMP1 and PUMP2, holds a pump on until you stop it or unplug 12 V.