HEM Data Products

OBD Mini Logger™

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DAWN Mini-Logger Video

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The DAWN OBD Mini Logger™ is a compact, low-cost data logger to acquire CAN bus data from cars and light trucks. The logger installation is simple since it snaps directly on the J1962 OBD connector. The logger is so small that it fits in the palm of your hand.

DAWN comes standard with a generic OBD-II database which defines almost 100 parameters according to the SAE J1979 standard; 40 being available on a typical car. The companion DawnEdit™ software determines which parameters are available on the vehicle to create a unique database for each vehicle model. The user can select which parameters are acquired. Also, the user can add custom messages and parameters in DawnEdit to acquire proprietary messages.

The OBD Mini Logger can simultaneously acquire four types of messages:

  1. Generic OBD-II – standard on all cars and light trucks after 1996 (mode $01) as defined by J1979
  2. Enhanced OBD – similar to a service scan tool database; specific to each OEM (mode $21 and $22)
  3. Normal messages – transmitted for normal vehicle operation; no request messages required (These can be any CAN format including J1939 and CANOpen)
  4. Direct Memory Reads (DMRs)- highly proprietary (mode $23); reads controllers’ memory

Acquiring Data Beyond Standard OBD-II Parameters…

Soft LED indicators show the logger status without distracting the driver. It has a real-time clock which the user can set to the local time zone. The Mini Logger includes a battery backup so the logger always maintains the correct time. The GPS model syncs the time with the GPS satellites automatically.

The DAWN Mini-Logger Video demonstrates how to configure the logger and convert the message to scaled, engineering parameters.

Standard Parameters

List of OBD-II parameters


OBD Mini Logger Specifications

ISO 15765-4 (CAN, 11-/29-bit, 250/500 kbps) Yes
SAE J1850 PWM & VPW Yes
ISO 9141-2 Yes
ISO 14230-4 (KWP) Yes

No. of Protocol Ports (Channels)

Three CAN channels (250, 500kbps, other)

Real-time PC data


RT Connections to PC


Stand-alone Logger


Store Messages


On-board Storage

4GB internal storage. 32 GB option. How to estimate data size

Auto Start-up


LEDs for status


Operating system

Proprietary RTOS

GPS (NMEA 0183)

Option. Internal to Mini Logger.

Wireless (WiFi)

Option. Internal to Mini Logger.

Cellular modem

Option. Internal to Mini Logger.

Real-time clock


Analog Inputs

Internal Temperature Sensor


3-axis MEMS Accelerometer

Option. +/-2.3 g. Resolution of .018g

Vehicle Battery Voltage



Optional ADAQ Mini


Size (inches)

Size (mm)

OBD Connector: 1.9W x 0.70H x 1.5L

48W x 18H x 38L

Supply Current:

80 mA. Up to 200mA with WiFi

Operating Temperature C

-40 to +70

Operating voltage

4 to 36V

Over/Under Voltage protection

100V including input capacitors to prevent a short circuit. Approved by several OEMs

Power Draw while sleeping

3 mA


1 Year


Data Storage & Transfer

The OBD Mini Logger comes standard with 4GB internal storage (up to 32GB option). Manually transfer message files to a PC using USB. The oldest file is removed if the logger runs out of disk space. How to estimate data size

Automated Data Transfers with WiFi and Cellular

WiFi or cellular are options to automate the file transfers to a website. Files are removed from the logger after a successful transfer. If you prefer to use an HEM Data website to store and display data click here for a description of features and benefits. For details on the WiFi and cellular options click here.


GPS data is an option for the OBD Mini Logger. GPS Data syncs with vehicle data on conversion. Click here for details on GPS that is housed within the Mini Logger.

Stand-alone Data Logger or Real-Time Display

If you need real-time display of the data on a PC or smartphone, then you can also use the OBD Mini Logger as a pass-thru device. We also offer a dedicated real-time device, the DAWN Mini Streamer™. The smartphone can then upload the necessary information over cellular to a website for summary and analysis. The Mini Streamer sends OBD, CAN and J1939 data.


Analog Data

The ADAQ Mini acquires analog data directly from sensors and outputs CAN data to an OBD or J1939 Mini Logger. Input types including voltage, current, temperature (thermocouple & thermistor), digital, frequency, PWM, and inclination. Click here for ADAQ details.


Hybrid Test Data

To learn about DAWN and hybrid test data see this page.

Future Enhancements

Check with HEM Data for availability for support of these future enhancements: Bluetooth, and smartphone.



Options include:



OBD Mini Logger J1962 Automotive Adapter


J1962 Pin J1962 Pin Description
1 Discretionary* (GMLAN SW CAN Line)
2 + line of SAE J1850
4 Chassis/Case Ground
5 Signal Ground
7 K Line of ISO 9141-2
8 Discretionary*
9 Discretionary* (GM ALDL)
10 - line of SAE J1850
11 CAN2-, (GMLAN MS CAN L), Short to ground
12 Discretionary*
13 Discretionary*
14 CAN-  (GMLAN HS CAN L), Short to ground
15 L line of ISO 9141-2
16 Unswitched Vehicle Battery Positive


Logger Comparison

Feature OBD Mini Logger J1939 Mini Logger
16 pin J1962 OBD Connector Yes Needs an adapter cable
9 Pin J1939 Deutsch Connector Needs an adapter cable Yes
CAN channels (networks) 2 Version 3=1; version 4=2
OBD-II J1979 support Yes No
J1939 Support Yes Yes
J1708 Support (older HD protocol) No Yes
Legacy OBD protocols Yes No
Raw CAN (Normal messages, CANopen) Yes Yes
Cellular Yes No
WiFi Yes Yes
GPS Yes Yes
External uSD card for data storage Version 3 Version 3 & 4
Internal data storage only Version 4 No

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DAWN Mini-Logger Video

Have a question? Please see our FAQ.

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