Digital Loggers


Frequently Asked Questions for DIN Relay IV

Updated 03/13/2020

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

From $159!  Order now - call (408) 330-5599.

What are the latest new features?


How do I set up network access in Windows? From a Mac? - Thanks to John McClintock for these MAC tips.
Do I need a crossover cable?
On initial setup, I can't establish a Ethernet communications from a Windows PC.  Help!
What is the default IP address?  How do I reset to defaults
What is the default password?
How do I set up port forwarding? Here's a specific Linksys example? -Thanks to Mike G.
What is the default IP address?
How do I reset to defaults
How do I use the keypad to set it up?


How can I control higher-current loads?
What is the polarity of the connectors?
How can I power the DIN relay itself?
Basics: What's a relay? How can I wire it up? Applications?  Do you have a mechanical drawing?
How do I connect the ADC inputs?
What are the connector specifications?
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 are the contact ratings?
What wire should I use?
How should I torque the terminals?
Can you develop custom hardware for my application?
Do you have a ruggedized version? Something suitable for mobile use?
How can I expand EEPROM to store scripts on earlier models? (DIN, DIN2, DIN3)

General FAQs

What is the current firmware version?
What's the new Lua Language and Scripting all about?
How do I enable AutoPing?
Can you explain the auto-ping settings?
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?
Can I invert AutoPing or the web page linksto use the NC contacts?
Can you explain the auto-ping settings?
What are the CRITICAL and PROTECT functions?
Where can I find the manual or spec sheet for the earlier model?

External APIs - Communicating with the power controller

How can I access the switch from my own application or remote script?  What's the cURL API?
My program ran fine on an earlier DIN relay, but doesn't connect now.  Help!
Is this product compatible with legacy plaintext scripts and http control?
How can I control the switch from my own applications? 
What is the recommended REST API?
How can I connect to Amazon Echo, Alexa, Dot or Tap products?
How can I connect to Google Assistant or Google Home?
Have any SNMP setup tips?
Do you support MQTT?
Do you support MODBUS?
How can I set up IFTTT?
Have "One Liner" examples using cURL?
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 a perl script from LabView?
Where can I find iPhone, iPad, or Android apps for Digital Loggers?
Do you support PowerMan?


    What's the Hardware Revision History?


A:      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 Lock Out) 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 for DH11 or DS18B20 type sensors
  • Two ADC inputs scaled 0-10V and 0-100V
Note: version 4 supports input supply voltages from 12 to 28VDC. If you require 48V or AC mains power, please contact sales for a variant product.
RS-232 has been removed in lieu of the sensor port and ADC inputs.

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

Question:        What is the polarity of the connectors?

Answer:          The polarity is stamped above the conenctor. It may be eeasier to see if they are removed.

        What are the contact ratings?

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

Relay Contact Ratings
















Relays are 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

    How do I connect the ADC inputs?
A:    Remove the accessory hatch. The plastic hatch on the right side of the relay can be opened to add a WiFi antenna or to connect analog inputs. Using a small screwdriver, press gently on the lower edge of the hatch. Push towards the buttons The hatch will flex and pop open.

The antenna and/or ADC connector may be attached when the hatch is removed. A three pin connector is provided for ADC input. The upper pin is scaled for 0-100VDC, and the lower pin is 0-10VDC. The center pin is a ground reference bonded to the negative power input.

        What are the power requirements?

A:  The relay dissipates an absolute maximum of 5.8W during switching with all relays on.   Typical dissipation with relays off is 1.2W.  Although the case is well ventilated, ambient air temperature should not exceed 170°F for maximum reliability.  Surges over 35V may trip the safety fuse. 

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)
<10.5 UVLO 0.001
12 0.100 1.200
14 0.086 1.204
16 0.076 1.216
18 0.073 1.314
20 0.063 1.260
22 0.060 1.320
24 0.056 1.344
26 0.055 1.430

DIN IV Power Requirements - All On
DC Volts I (Amps) Power (W)
<10.5 UVLO 0.001
12 0.515 6.180
14 0.440 6.160
16 0.385 6.160
18 0.344 6.192
20 0.312 6.240
22 0.284 6.280
24 0.260 6.240
26 0.241 6.266

 The input is protected by a PTC thermal fuse and SCR crowbar which trips around 35V.  If the fuse blows, correct the over-voltage condition and let the PTC cool to reset.

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:.

-- Open the Blinds
function open_blinds()
Try it at  admin/4321
You can also trigger scripts remotely. More on that here.

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

A:           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. 

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

A:       Download a top-level print here (.pdf).  Here are graphics of the front and back of the relay.

Q:    What is the current version of firmware?

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

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

A:     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 deeply discharged.

Q:     Is this product compatible with the older (less secure) HTTP plaintext command syntax?

A:       To use the earlier HTTP commands described here and CURL scripts that use plantext login, you'll need to enable this legacy setting on the SETUP page:

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

A:         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. After about 5 seconds, you will hear a bbeep, 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". 

If all settings are reset (the two last 'wipe' reset modes), the Subnet Restriction will be enabled to prevent remote access using the default password. ONLY MACHINES IN THE SAME SUBNET WILL BE ABLE TO CONNECT AFTER RESETTING TO DEFAULTS.
Besides setting your computer to a compatable network, you can also use the keypad to set it up.
Q:                Wiring and terminal information?

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

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

A:       Follow the instructions in this document.

Q:     Can you explain the auto-ping settings?

A:   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.

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

A:          The REST API is the best place to start.  For plaintext HTTP use, 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.

Q:      Can you develop custom firmware for my application?

A:     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.   

Q:    Can you develop custom hardware for my application?

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

Q:       Do you support PowerMan?

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

Q:      What's a relay?  How can I wire it up?

A:      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:

Find a nice group of relay application notes and wiring examples here:



Back To Top


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. 2005-2019.