Frequently Asked Questions for DIN Relays V4


   Download a printable manual       Check the spec sheet.     Legacy versions V1 V2 V3
$169 or less.  Order now - call (408) 330-5599.

Frequently Asked Questions

What's new in the product?
What is a relay? How can I wire it up?
How can I control higher-current loads?
How can I power the DIN relay itself?
What's the new Rest API?
How do I set up network access from Windows? ... from a Mac? - Thanks to John McClintock
How can I access the switch from my own application or remote script?  What's the cURL API?
How do I set up a router to port forward for Internet access? -Thanks to Mike G.  Find more specific port forwarding examples here.
What are the contact ratings?
What is the power dissipation?  What are the power requirements?
What size terminals should I use? Which wire gauge should I use?
I'd like to build a DC / solar powered IP Cam, WiFi AP, or similar DC powered system.  What components do I need?
What's the Lua scripting language all about?
What's syslog?  How can I keep an event log?
How can I momentarily pulse a relay?
How do I use Wake on Lan?
What are the mounting hole dimensions?
Do you have a ruggedized version? Something suitable for mobile use?
What is the default IP address?
What wire should I use? How should I torque the terminals?
How do I reset to defaults
What is the default password?
On initial setup, I can't establish a Ethernet communications from a Windows PC.  Help! Do I need a crossover cable?
How can I send HTTP requests?
Can you develop custom firmware or hardware for my app?
Can I invert AutoPing or the web page links to use the NC contacts?
Do you support PowerMan?
Can you explain the AutoPing settings?
What are the CRITICAL and PROTECT functions?
While we recommend upgrading to the RestAPI, we do have simpler HTTP based  Visual Basic.NET, Python,  C++ and .NET programming examples.  There are also Java and compiled Windows command line Perl examples.

Question:        What's new in this product?

Answer:           In our second version, DIN Relay II, with serial numbers DIN22000 and higher, we added these features:

  • Relay anti-chatter protection.  Maximum relay switching frequency is limited to ~2Hz for safety and longevity.
  • Variable coil current control.  Relay holding and pull-in currents are regulated for improved efficiency.  Power consumption has been reduced by more than 40% from earlier models.
  • Watchdog supervisor.  We've added a second processor which continuously monitors the microcontroller and reboots it gracefully if necessary.
  • Increased memory. Non-volatile memory has been increased from 16kb to 256kb.  No memory expansion board is required for script storage.
    Find the DIN II manual here.

In version 3.0 of  DIN Relay III, we added these features:

  • DC input voltage rating now increased to 48VDC
  • Added audio alarm-beeper
  • Added 2x16 LCD display to display status and help with setup.
  • Added internal real-time-clock with NTP and local time synchronization
  • Numerous firmware upgrades including scheduling feature , increased AutoPing speed limit and added more scripting commands.
  • Increased relay contact rating and durability
  • Added keypad for local control
  • Updated rating, testing, and specifications for higher DC input voltages
  • Eliminated the internal RJ-45 bulkhead for more reliable connection to unshielded RJ-45 plastic plugs. Connection status displayed on LCD.
  • Case color has changed, manual and box are updated, power consumption has increased slightly

In version 3.1, we added these features:

  • Added RS-232 web console for remote machine control. The +5 supply has been removed.  RS-232 has 2.5kv isolation and is brought out to three screw terminals in the upper right hand corner.
  • Added internal UVLO (Under-Voltage LockOut) for more reliable operation on battery power.  UVLO starts at 11.5V and shuts off at 10V to prevent battery damage.  This feature is designed to augment an existing UVLO/OVP charge controller in battery powered applications.  It is not a substitute for a solar/wind charge controller and doesn't guarantee proper reset of attached devices in the event that a battery is highly discharged.
  • Minor internal improvements.
    Find the legacy DIN III manual here.

Version 4 (currently shipping) was a complete redesign adding these features:

  • Faster processor with 2.4GHz WiFi, SMA antenna. WiFi or hardwired Ethernet, can be selectable by admin.
  • Over-current protection fuses on all relay common lines for safety
  • Changed to 3 pin pluggable screw terminals for easier wiring
  • Changed input operating voltage range to 12-28VDC. Contact if you prefer 48V or PoE.
  • Added more rugged SCR Crowbar over-voltage protection (OVP) with thermal self-resetting fuse. Kept the 11.5V under-voltage lockout (UVLO)
  • Removed RS232 in lieu of RJ-11 style TTL I/O jack suitable for connecting DS, DHT or SHT series temperature / humidity sensors.
  • Added dual ADC inputs 10-bit, 0-10V default.
  • Upgraded thermoplastic enclosure.  New external dimensions 2.320 X 4.350 X 6.088 "
  • Vast memory expanbsion permits additional software features including: RestAPI, SNMP, Notifications, SSH, SSL, HTTPS
    Find the current DIN4 manual here.

Tell us what you'd like to see in the next version -

Question:        What are the contact ratings?

Answer:           All eight internal T-90 Relays have the following ratings:

Relay Contact Ratings










240VAC 35A 25A




Relays are rated at 250,000 operations MTBF at 50% load.  800,000 operations at 10% load. Case terminals are rated at 12-15A, depending on agency.  Only stranded wire of appropriate gauge should be used.  Here are some wiring suggestions. Use stranded wires only. Note that the common lines on all relays are internally fused at 12A. Lost or damaged terminal?  No problem. Contact

Question:        What are the power requirements?

Answer:  The relay dissipates an absolute maximum of 5W during switching with all relays on.  Power dissipation decreases with input voltage due to the use of an efficient switching power supply. Typical dissipation with relays off is 2W.  Although the case is well ventilated, ambient air temperature should not exceed 140F for maximum reliability.  Surges over 32V may trip the SCR crowbar.  Power must be disconnected to reset.. 

The relay will shut down at input voltages below 11VDC. If you expect to encounter brown-out conditions in your application, set the Power-on-Recovery Mode on the setup page for safest operation.   Please read the UVLO and OVP suggestions below.

Add an external MOV, snubber, or other protection device across the power input terminals in noisy environments. Read more at

DIN4 Quiescent Power Requirements
DC Volts I (Amps) Power (W)
12 0.250 2.00
24 0.211 1.90
28 0.191 1.91

Add 2.5W (30mW/relay) when all eight control relays are ON.

 The power input  is protected by an auto-resetting polyfuse PPTC.  Over-voltage will thermally shut down the polyfuse.  Remove the load and allow 60 seconds for the fuse to cool and reset if this occurs. 

Question:        Can I invert AutoPing or the Web Page to use NC contacts?

Answer:           For safety reasons and to prevent support issues, we have not implemented an "invert relay" function in either the web UI or AutoPing.  You can drive the relays in reverse by:

  • Setting up a script to turn a relay -on- in the event of an AutoPing failure.  For example  Line 2:  "ON 1"
  • Use the AutoPing event to trigger the script (enter the line number ie 2 of the script for that Autoping IP).

You can also use the programmable web links to start a script.  For example, a link like "CIRCUIT 1 OFF", could be lined to a script 2. ON 1, 3. END.  This inverts the "OFF" operation by closing the relay.

Question:        How can I mount to a panel?

Answer:           Mounting holes are located on 5.8x3.9" square centers with clearance for #6 screws. 

What components do I need to build a remotely powered DC site using the DIN relay as a power controller?

Answer:     In addition to the load (ie. APCam, PtP link, AP, etc), you'll need a battery, some source of power, ie wind or solar, and most importantly a charge controller with OVP and UVLO features.  Over Voltage Protection is needed for reasonable battery life.  Under Voltage Lockout is needed to correctly reset attached devices as well as the DIN relay and to prevent oscillation when the battery is nearly discharged.

Question:     What is the default IP address?  How do I reset to defaults?  What is the default password?

Answer:         If you have lost the IP address or admin password, follow this procedure to reset to the default IP address of

  • Using a small stylus, press and hold the reset button for 5 seconds to enter the reset menu.  Select the network reset option.

The default master login is "admin" and default password is "1234".  This procedure resets the admin login and IP address and lockout, but doesn't affect outlet names and links.


Question:        Wiring and terminal information?

Answer:           Use stranded wire from 28AWG to 12AWG.  Check this wiring table for recommendations.

Question:     On initial setup, I can't establish a Ethernet communications from a Windows PC.  Help!

Answer:       Follow the instructions in this document.

  • Question:        How can I control the switch from my own applications? 

    Answer:           The recommend method is using the Rest API -   If you prefer custom  Download the latest User Utility which includes PowerMan support for Linux. Your application can use HTTP communications.  Note that using HTTP is generally less secure than the RestAPI.  Here are some HTTP examples with source.  Windows users can download a Perl interpreter to run scripts. 

    Question:        Can you develop custom firmware for my application?

    Answer:           Gladly. We've done this for many customers. This is most practical for orders of 500+ units.  Generally there is an NRE, but in some cases labor can be amortized.; After agreeing on a -very specific- project description,
    we can send you an estimate of the time involved to code, debug and test.

  • Question:        Can you develop custom hardware for my application?

    Answer:           Gladly.  We've done this for many customers.   Please call with your requirements.

    Question:        Do you support PowerMan?

    Answer:           Yes, absolutely.  The latest code is here: Download the latest User Utility here.

    Question:        How can I momentarily trigger (pulse) a relay?

    Answer:          Two examples:

    Just wire a capacitor in series with the circuit (assuming a DC load).  Simple.

    Click "Cycle"
    Press the existing cycle button in combination using the NC contact (instead of NO):


    Custom Script
    Name your circuit here:

    A third alternative is triggering a Lua script remotely.


    Question:        What is a relay?  How can I wire it up?

    Answer:           The DIN relay has dry contact FORM-C outputs.  They provide whatever output voltage you connect to them.  For example, if you connect a wire from the positive side of your 24V supply to the COM terminal, then the NO terminal will provide 24 volts when the relay is switched on, and the NC terminal will provide 24V when the relay is off.  You can operate the DIN relay on a different voltage than the relay contacts.  For example, the DIN relay could run on 12VDC, but switch 220VAC.  You can also use the relay to switch data, phone lines, or other electrical signals.  In a relay, contacts are electrically isolated from the coil.  The DIN relay controls the coil in the diagram below:

    N.O. means Normally Open
    N.C. means Normally Closed
    COM means COMmon

    Each relay is fully isolated, there is no internal connection between the relays.

    A relay schematic looks like this:
    Find relay basics here:


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    If we haven't answered your questions here, please call (408) 330-5599 or send us an email.  We'll be glad to help.

    Digital Loggers, Inc. 2005.