Teach your gripper what a grip feels like.
GripSense sits inline on the servo gripper you already own. Hold the teach button, close on nothing, close on a real object, and it learns the difference. From then on it tells your controller what happened: nothing gripped, holding, or jammed.
Pre-launch. Sensing concept bench-validated; PCB design in progress.
Brief inrush as the servo moves, then current falls back to idle. No sustained rise, so no grip is reported.
- Works with the servo you already ownStandard 3-wire hobby servos. No proprietary smart servo, no platform lock-in.
- No code to writeTwo button presses stand in for thresholds, debouncing and control logic.
- Protects the servo and the objectThe servo never sits in a stall, and a soft object never gets crushed.
Position control has no idea what it grabbed.
A hobby gripper is driven by telling a servo to go to an angle. The servo doesn't know whether it closed on air, on a block of aluminum, or on an egg. It drives toward the commanded position and keeps straining until something gives.
The servo burns out
Blocked by a rigid object, the servo fights a position error it can never close. Sustained stall current overheats the motor and strips the gears. This is one of the oldest, best-documented failures in hobby robotics.
The object gets crushed
Anything soft or fragile deforms long before the servo feels meaningful resistance. By the time position control notices anything, the damage is done.
The usual fix is a project of its own. Add a current sensor, sample it fast enough, tell inrush apart from stall, pick thresholds in milliamps, debounce them, and write the control logic. GripSense replaces all of that with a button you hold while you close the gripper twice.
What the bench tests showed
With a high-side current sensor inline on the servo's power wire, three grip cases separated cleanly.
Gripping nothing
No sustained current elevation. Current decays back to idle once the move completes.
Gripping a pliable object
A clear current spike, roughly four times smaller than the hard-object signature, and clearly above the free-motion baseline.
Gripping a hard object
A large overcurrent signature, the well-known stall condition that cooks servos.
Detecting a hard stall was never the hard part. A blocked servo drawing several times its running current is textbook. The open question was whether a compliant grip produces a signal you can separate from both free motion and a stall.
It does, and by a wide margin. That is the result that makes a teach-once, no-thresholds module possible: the three cases live far enough apart that GripSense can record your gripper's own signatures and classify from them, rather than asking you to guess a current limit.
separation between the pliable-object signature and the hard-object signature on the bench
Two button presses, then it just works
-
Wire it in
GripSense sits inline on the servo's power wire. The PWM signal wire passes straight through, so your existing controller keeps driving the servo exactly as before.
-
Teach it
Hold the teach button. Close the gripper on nothing, then close it on a representative object. GripSense records the free-motion baseline and the grip signature itself.
-
Run
Command the gripper closed as usual. GripSense watches for contact and reports a hold instead of a squeeze. If it sees a jam or stall, it flags a fault.
-
Read the result
An RGB LED shows state on the module. A protected digital output feeds your microcontroller's input pin, so you branch on HIGH or LOW instead of interpreting raw current.
No code. No PID tuning. No threshold math. No configuration app.
GripSense monitors and reports. It never drives the servo's position, so nothing about your existing control loop changes.
What's decided, and what isn't
One small box, inline on the servo lead
Three-wire servo lead in, three-wire servo lead out. A teach button and an RGB status LED on the lid. A header on the side for the digital output and I²C. Everything lives in a Polycase LP-21PMBR: flame-retardant ABS, UL94-5VA rated, with PCB mounting bosses and a recessed cover, machined for the connectors.
- Sensing
- High-side current sensing inline on the servo power line (INA219-class sensor in prototyping)
- Servo signal
- PWM passes through untouched. GripSense monitors and reports; it does not command position
- Servo compatibility
- Standard 3-wire hobby servos. No proprietary servo, no platform lock-in
- Controller
- ESP32-class microcontroller
- Teach
- Physical button, press-and-hold to enter teach mode
- Local indication
- RGB status LED (common cathode)
- Host output
- Protected digital output for direct wiring into a host controller's digital input
- Data interface
- I²C for live current and state data, and for logging
- Enclosure
- Polycase LP-21PMBR, CNC-machined for connector cutouts
Not decided yet
- Final price
- Exact current range and supported servo classes
- Whether the firmware will be open source
- Connector types
- Availability date and shipping timeline
These get filled in as the PCB design closes. Reserve a spot and you'll hear as each one lands.
Built for the grippers people actually use
Servo grippers are close to a default part in hobby robotics, which is exactly why a universal module makes sense.
- Open-source desktop armsLow-cost arms whose grippers are driven by a stock hobby servo.
- Hobby arms and clawsGripper kits and generic acrylic or laser-cut claws on a single servo.
- Education and competitionClassroom robotics and competition claw mechanisms.
- Maker automationPick-and-place rigs, small automation cells and animatronics with servo-driven grippers.
What else is out there
Force-aware gripping isn't a new idea. Here's what exists and where GripSense fits.
| Product | What it does | How GripSense differs |
|---|---|---|
| Waveshare Gripper-B | Constant-force control that stops before crushing; reports load, current and temperature. | Requires Waveshare's proprietary serial-bus smart servo. GripSense works with the servo you already own. |
| Annin Robotics AR4 gripper kit | Bundles a servo, board and current-limit sensor. | Tied to one robot arm platform. GripSense is platform-independent. |
| Sensorimotor (Tindie) | Turned a plain servo into a smart device reporting position, current and temperature. | Discontinued and no longer available. |
Where the project stands
This is a pre-launch page, not a storefront. Here's the honest state of things.
-
Done
- Bench feasibility validation of the core sensing concept
- Three-state separation confirmed: nothing, pliable, hard
-
In progress
- Enclosure selected (Polycase LP-21PMBR)
- Moving into PCB design with a hardware collaborator
-
Not yet
- Production PCB
- Feature-complete firmware
- Manufacturing, pricing, availability
Who's building it
Max Bean-Tierney is a mechanical engineering student at Brown University. He is the lead engineer on the gantry and control systems for an automated microfluidic liquid-handling instrument, work that includes custom Marlin firmware on an STM32-based controller, a hand-written I²C driver for a Honeywell pressure sensor, and a closed-loop pressure controller with adaptive feedforward and anti-stiction compensation holding to about 0.15 psi. He is a patent-pending co-inventor on an electroosmotic flow cell device and has presented at the SLAS International Conference.
The electronics and PCB are being developed with a hardware collaborator.
GripSense is an independent personal project. It is not affiliated with Brown University or Revvity.
Reserve a spot for the first run
Preorder checkout isn't open yet. Leave your email and you'll be first to hear when it is, along with the price and the supported servo range as they're finalized. No payment today.