Digital Loggers


Frequently Asked Questions for DIN Relay IV


Download the online manual.   Download a printable manual.    Check the spec sheet.

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Frequently Asked Questions

How can I control higher-current loads?
How can I power the DIN relay itself?
Basics: What's a relay? How can I wire it up? Applications?
What are the latest new features?
Do you support MQTT?
How do I set up network access from Windows? from a Mac? - Thanks to John McClintock for these instructions
How can I connect to Amazon Echo, Dot, or Tap?
How do I set up port forwarding?
What is the new RestAPI?
How can I access the switch from my own application or remote script?  What's the cURL API?
What's the new Lua Scripting Language all about?
How does the relay communicate via HTTP?
How do I enable AutoPing?
My program ran fine on the DIN Relay III, but doesn't connect now. Help!
What's syslog?  How can I keep an event log?
What is the default IP address?  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!
How can I control the switch from my own applications? 
Can you develop custom firmware for my application?
Can you develop custom hardware for my application?
Is this product compatible with legacy plaintext scripts and http control?
Can you explain the auto-ping settings?
Do you have a Visual Basic.NET example program?  Thanks to Alan Holmes
Do you have a C++ programming example?
Do you have a .NET programming example?
Do you have a Java programming example?
Do you have a compiled Windows command line tool or a Perl example?
Do you have a Python programming example?
Do you have a Crestron control module?
How can I run the perl script from LabView?
Where can I find iPhone, iPad, or Android apps for Digital Loggers?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 pluggable mating terminals / connectors should I use?
What wiring 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 Scripting Language all about?
What's syslog?  How can I keep an event log?
How can I momentarily pulse (or reverse cycle) a relay?
How do I use Wake on Lan?
What is the current firmware version?
Do you have a ruggedized version? Something suitable for mobile use?
What is the default IP address?
What wire guage 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 control the switch from my own applications?   
How can I send HTTP requests?
Do you support PowerMan?
Where can I find the manual or spec sheet for the earlier model?

\What's new in this product?

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.

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.

In version 4, we completely redesigned the unit and added a host of new features:

  • Pluggable Pheonix connectors on all lines
  • Fuses on relay common lines
  • Power supply OVP with replaceable fuse
  • WiFi
  • SSL, SSH, RestAPI, extensive logging.
  • Lua scripting
  • OVP with replaceable fuse
  • Temp/humidity sensor port
  • Note: version 4 supports input voltages from 12 to 28VDC. If you require 48V or AC mains power, please contact sales for a variant product.

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

What are the contact ratings?

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

Relay Contact Ratings
















Relays are RU and CE component approved, and rated at 250,000 operations MTBF at 50% load.  Case terminals are rated at 8-12A, depending on agency.  Only stranded wire of appropriate gauge should be used.  Terminals must be well torqued, but not over 10in/lbs.  It is wise to recheck torque after completing the installation.  Heavy traces and gold plating are used to minimize internal resistance between the terminals and relay contacts, typically 25m Ohms, so internal contact power dissipation is not normally a consideration. For maximum flexibility, relay contacts are unprotected.  For high current inductive switching, consider adding an external snubber circuit to extend contact life. Download contact protection information from

Can it handle large inductive loads?

Download contact protection information from

What are the power requirements?

The relay dissipates an absolute maximum of 5.8W 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 170°F for maximum reliability.  Surges over 40V P-P may damage the internal regulator. 

The relay will shut down at input voltages below 10.5VDC. If you expect to encounter brown-out conditions in your application, set the Power-on-Recovery Mode on the setup page for safest operation.  To prevent oscillation, a brown-out re-latch function is also provided on the Setup page. In the event of a brown-out, you may specify a time period after which the relay will attempt to re-latch the contacts. This function is disabled by default and has no effect if the relay is properly powered.   Please read the UVLO and OVP suggestions below.

Add an external MOV or other protection device across the power input terminals in noisy environments.  We are working hard to make this the most efficient product in its class.

DIN IV Power Requirements - Idle
DC Volts I (Amps) Power (W)
<11 UVLO 0.003
12 0.151 1.81
14 0.129 1.81
16 0.114 1.82
18 0.101 1.82
20 0.092 1.84
22 0.082 1.80
24 0.073 1.75
26 0.061 1.59
DIN IV Power Requirements - All On
DC Volts I (Amps) Power (W)
<11 UVLO 0.003
12 0.341 4.09
14 0.315 4.12
16 0.287 4.15
18 0.231 4.16
20 0.207 4.14
22 0.182 4.00
24 0.162 3.89
26 0.151 3.93

 The input is protected by a 1A fast-blow fuse and SCR crowbar which trips around 31V.  If the fuse blows, correct the over-voltage condition and replace it with a similar 1A fuse. Call us if you need spare fuses or terminals.

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

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:

You can also use the programmable web links to start a script. 

What are the mounting dimensions and physical size? Do you have drawings?

 Mounting holes are located on 5.308 x 1.968 centers.   Download a 2-D print of the cover here (.pdf).  Here are graphics of the front and back of the relay.

What is the current version of firmware?

The current version is  on the update page  Find the revision history here, and firmware update instructions here.

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.

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

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

  • Press the reset button, then use the up and down keys to choose the type of reset.
    The following reset modes are available:

    1. Clear lock bits: Clear protection bits only. Other settings are preserved.
    2. Reset network and scripting: Clear protection bits, reset network settings and admin login, disable autoping and scripts. Other settings are preserved.
    3. Reset network and scripting + enable Wifi: Clear protection bits, reset network settings and admin login, disable autoping and scripts, and enable open WiFi access. Other settings are preserved.
    4. Complete wipe: Reset all settings to factory defaults and remove any user files. All settings will be lost!
    5. Complete wipe + enable WiFi: Reset all settings to factory defaults and remove any user files, then enable open WiFi access. All settings are lost!

    To activate the selected reset mode, press cycle or the reset button and hold it.

The default master login is "admin" and default password is "1234". 


Question:        Wiring and terminal information?

Answer:           Use stranded wire from 28AWG to 14AWG.  Find information on Phoenix connectors here.

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

Answer:       Follow the instructions in this document.

Question:     Can you explain the auto-ping settings?

Answer:   The following parameters are used for AutoPing operation:

  1. Time between pings: This is the time between each ping check of the IP address. 60 seconds should be useful for most applications. If multiple AutoPings are in use, each IP will be checked in sequence. For example, 2 autoping IPs and a setting of 60 seconds will cause each IP to be checked every 120 seconds.
  2. Ping failures before reboot: This sets the number of failed communication attempts that must be sequentially detected before a task is executed. For example, when set to 5, the target system must fail to respond 5 times in a row before it is rebooted. Since occasional network overloads and missed packets can occur during normal network operation, a number between 5 and 10 pings is recommended.
  3. Ping responses to enable autoping: To ensure a reliable connection, autoping will only be enabled after this many successful pings. We do not recommend changing this (10 is default) unless you must configure your controller before connecting it to the target devices.
  4. Times to attempt reboot: If you have an unreliable target device, limit the number of times it will be rebooted by entering that value here. For example, entering 5 will execute the task up to 5 times before giving up.
  5. Device reboot delay: After rebooting a device with a cold-boot power-off, a waiting period should occur before the IP address is re-checked by AutoPing. This delay allows the device to reboot. Windows and Linux servers can force automatic file system checks which may take several minutes to complete. Enter a safe value here, for example entering 600 would cause the power controller to start checking the server for normal operation 10 minutes after reboot. If a script is to be triggered, any delays contained in the code being executed should be considered in determining the delay setting here so that the thread completes before the delay elapses. This timer starts at the execution of the thread started.
  6. Handle failures immediately instead of waiting for timeout: Rather than waiting for the ping responses to enable autoping trial, the device is rebooted immediatly upon failure.
  7. Activate enabled entries without trial on service restoration: After a power restoration or if autoping is disabled / enabled from the "Enable AutoPing" checkbox, assume trial has passed.

Find a more detailed description of Auto-Ping here.  Find instructions on modifying Auto-Ping behavior using scripting here.

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

Answer:            Download the latest User Utility which includes PowerMan support for Linux. Your application can use HTTP communications. There are programming examples from several languages listed in the top section.

Windows users can download a Perl interpreter to run the script version.  This script is compatible with all DLI power controllers.

Question:        Can you develop custom firmware for my application?

Answer:         Gladly.  We've done this for many customers.  Our programming rate is $75/hour.  After we agree 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 expand EEPROM to store scripts?

Answer:           If you have an early DIN relay (first model with a serial number below DIN22000), you'll need expanded memory.  A 256K bit EEPROM option is available, P/N 256EE.  This is a factory installed PCB, so you'll need to send the early unit back to DLI for upgrade.  If you have the new DIN Relay II, with serial number DIN22000 or higher, 256K of non-volatile memory is already installed.

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

Answer:          Three 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:

create a button that starts a script starting on line #2:

Clicking "Open the Blinds" toggles pulses the relay per this script:.

Try it at  admin/4321
You can also trigger scripts remotely. More on that here.


Question:        What's 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, communications 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. The word "common" describes the wiper of the relay itself which shares the NO and NC contacts in common. The COM pins on the DIN relay are not connected each other unless you elect to do so externally. Put simply, all relays are fully isolated.

A relay schematic looks like this:

Here's a link to some nice wiring and application notes for relays.


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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.