The $99 ESP32 industrial bench

You don't need a $4,000 IoT gateway and a six-week PoC to see whether unified observability is going to work for your factory. You need one ESP32-S3, three real signal types on a breadboard, and a dashboard you didn't have to host yourself. That is the bench kit.

It is a deliberately small piece of hardware with a deliberately big claim: in 30 minutes, with parts that cost us roughly $28 in components and ship as a $99 kit, you can put a real 4-20 mA sensor, a real I2C temperature/humidity probe, and a real digital dry-contact onto a Sutrace dashboard hosted in europe-west3. No gateway server. No site visit. No vendor lock-in story dressed up as a "platform".

If you've been burned by the usual "industrial IoT starter kit" — the ones that read fake demo data from a JSON file and call it a proof of concept — this is the opposite of that.

What's in the box

A pre-flashed ESP32-S3-DevKitC-1 (the WROOM-1 variant, 8 MB flash, 8 MB PSRAM). A breadboard. Dupont jumpers. An SHT45 breakout on I2C for temperature + humidity. An INA226 breakout for high-side current/voltage measurement. A 165 Ω 1% precision resistor (the magic value for 4-20 mA into ESP32 ADC). A 4N25 optoisolator and pull-up resistor for one digital dry-contact channel. A USB-C cable and a 5V/2A wall plug.

That is it. No PLC. No managed switch. No proprietary "edge gateway". The whole thing fits in a padded envelope and runs off a wall socket.

What you actually do with it

You plug the ESP32 in. It boots into a captive-portal commissioning mode — your phone joins its open WiFi and you fill in three fields: site WiFi SSID, site WiFi password, and the device-claim code that came on the kit's card. The device flashes once, joins your network, and registers itself against your Sutrace tenant via MQTT-over-TLS to our EU-resident broker.

Within about 90 seconds of that, you have a row in your Sutrace overview labelled with the device name you picked. The temperature and humidity from the SHT45 are streaming at 1 Hz. The INA226 is reporting bus voltage and current draw of the ESP32 itself (a useful sanity-check signal). The 4-20 mA channel is reporting whatever you wired into it — most people use the 0.66 V to 3.30 V range to bench-test a real plant sensor before they wire it on the line.

No firmware to compile. No certificates to copy around. No Mosquitto to install on a Raspberry Pi.

Why this matters for the rollout decision

The bench kit isn't the product. The mid-market industrial monitoring rollout is the product — typically three to twelve sites, real Modbus and OPC UA devices, real PLCs, real compliance scope. The bench kit exists because that rollout is a six-figure decision and we'd rather you make it after seeing live data than after a deck.

It also lets you answer the questions that actually decide rollouts. Does my IT team's egress firewall let MQTT-over-TLS out to europe-west3? (You'll know in 90 seconds.) Does our existing 4-20 mA pressure transmitter sit in the linear range when read through this circuit? (Wire it in and look at the chart.) Does the Sutrace alerting actually wake someone up at 03:00 when the signal trips? (Force a trip and find out.)

Those are the questions a bench kit can answer that a sales call cannot.

Limits of the bench

Some things this kit deliberately does not do, and you should know that going in.

It is single-tenant on purpose. The ESP32-S3 is wired to publish to one tenant. If you're evaluating Sutrace from multiple business units, you need one kit per tenant.

It is not Modbus-RTU out of the box. The kit ships with the three input types most useful for bench-evaluating a factory observability deployment — analog 4-20 mA, dry-contact, and I2C. Modbus RTU over RS-485 is supported in the firmware (we have a 30-minute Modbus walkthrough post) but you'll need to add a MAX485 transceiver and wire to a 120 Ω terminated bus.

It is not certified for hazardous areas. Don't put this in a Zone 1 environment or anywhere a fault could ignite something. The bench kit is for a desk, a lab, or a non-classified mechanical room where you're proving out a signal chain before you spec the real hardware.

It runs on USB power. Five volts at two amps over USB-C is fine for a desk. For a real install you want a DIN-rail 24 V supply and a buck converter, which is documented in the pillar tutorial — but that's the next post, not this kit.

What it costs

The kit is $99 including shipping inside the EU. We honestly tell you what it costs us to assemble: roughly $28 in parts (the BOM is published). The margin pays for the hours of test-fixture work, the pre-flashing, the captive-portal firmware, the support time we put in if you can't get past the WiFi step, and the EU-resident dashboard backend you're streaming into. We're not pretending this is a hardware business. It's a software business with a useful onboarding ramp.

The Sutrace dashboard tier the kit registers against is free for the first 30 days, then it rolls into the Bench plan ($19/month) unless you upgrade to a real site plan. Nothing locks. Nothing self-renews silently. The data is exportable and the device is unbrickable.

How to order

Email bench@sutrace.io with a shipping address in any EU member state, the UK, Switzerland, or Norway. We ship within five working days. Outside that footprint we'll do it but the courier costs eat the margin and we'll quote you separately. Bulk orders for evaluation across multiple plants — five or more kits — get the unit price down to $79 and ship from a single carton.

FAQ

Does the bench kit data go anywhere outside the EU? No. The MQTT broker, the device registry, and the dashboard storage are all in europe-west3 (Frankfurt). Authentication uses Firebase Identity Platform configured for EU residency. There is no US logging tier we forgot to mention. See the trust page for the architecture diagram and the DPA for the contract.

Can I use my own ESP32 instead of buying the kit? Yes — the firmware is available as a flashable image. The kit exists because most evaluators don't want to spend an afternoon sourcing parts and soldering. If you're an embedded engineer and you want to skip the convenience, mail us and we'll send the image and the wiring schematic.

What if I can't get past the WiFi commissioning step? We'll get on a 15-minute call and walk through it. The two failure modes we see are corporate WPA2-Enterprise networks (the ESP32 firmware supports them but you need the right user/cert config) and captive portals on guest WiFi (we have a workaround using the WPA2-PSK fallback SSID).

Does the captive portal work on iOS? Yes. iOS 15+ correctly autodetects the ESP32's open WiFi as a captive network and pops the commissioning page. Android 11+ also works. We've tested with the four most recent iOS and Android majors.

What sample rates does the bench publish at? Default is 1 Hz on all channels. The SHT45 is configured for 0.5°C/1.5%RH accuracy single-shot. The INA226 averages 16 samples per reading. The ADC channel oversamples 4x to reduce noise. You can change all of these from the dashboard; the device picks up new config on the next MQTT keepalive.

Can I add my own sensor to the breadboard? Yes — there are two unused ADC pins, one unused I2C address space, and three unused GPIOs broken out. The dashboard picks up new channels automatically once you publish on a new MQTT subtopic. The ESP32 industrial monitoring pillar tutorial walks through adding a Sparkplug B namespace if you want to be properly industrial about it.