How do I find the right relay for my application?

Which function is required?

  • There are 20 different time functions, which the ComatReleco time relays can perform.

Which partial time range must it be possible to set?

  • The smallest time which can be set with a time relay is 0.5ms (CSV4), the largest is 60 days (C55).

How do I set a time relay?

The process is the same for almost all time relays. First you select a function via the potentiometer. Each letter (A, E, W, K, usw.) stands for a specific function, which is described on the side of the relay or in the instruction leaflet.

Next you select the partial time range. The selected range always equals the maximum value. The fine tuning of the time is set with the last potentiometer. For example, this is how to set a 30 second switch delay:

Function: A

Partial time range: 60 seconds

Fine tuning: Then the potentiometer is set to 3 on a scale from 0-6 (6=60 seconds, 3=30 seconds, 1=10 seconds)

How can I convert an existing industrial relay into a time relay?

  • Industrial relays types C2 and C3 can be converted into time relays using time cubes. Simply plug in the time cube with the desired time function between the socket and the relay.
  • The sockets C12B0 and CS-155 (S5-M) have a module recess, which is intended to be used for time modules/monitoring modules. So you merely require a time module, which is plugable, in addition to a socket and an industrial relay.


Where do I find the programming software and all current drivers?

You can find the software in the download area of this website. Click here.

How do I install the driver for the USB converter correct?

Open the device manager. This cannot be found using the same path for each Windows operating system. You can search for “Device manager” directly in the search field via [START]. A yellow exclamation mark at the interface of the USB converter means that no suitable driver was found/installed. This means that you can search for the suitable driver manually and install it via right mouse click @ Features @ Driver @ Update driver. The yellow exclamation mark disapears after the successful installation.

Why don’t I have a connection via RS232 (& USB converter) to my PC?

  • The most common cause via USB converter is an incorrectly installed Windows driver. Make sure that the correct treiber is installed, delete the driver that was directly installed by Windows. The deactivate the automatic driver recognition of Windows. Only now can you install the driver correctly.
  • Ensure that you have administration rights on your account.

Why don’t I get a message (SMS) from the device although a signal is queued at the input?

First perform a diagnosis using the programme environment “FastSMSSet”. An error code is displayed in the field “Error code”. This is described in the data sheet along with the necessary action.

This can be due to the following; Wrong telephone number on file, no reception, SIM card blocked, no credit on the SIM card, communication error.

Why don’t the outputs switch even although I sent a message (SMS)?

There are several reasons why the switching of the outputs fails: No reception, SIM card blocked, telephone number not registered in the telephone book in FastSMSSet (only if number recognition is activated).

How can the GSM reception be improved?

  • By positioning the SMS relay, sometime jsut a few metres make all the difference.
  • Install an external beam antenna, which can be extended by a cable of up to 25m length (recommended maximum length).

To which length can the external beam antenna extended?

25m. This is the maximum lengthe we recommend. This results from the external beam antenna, which already has a 5 m cable, plus 20 m extension cable = 25 metres. Of course the anntenna can be extended further, however, this results in the GSM signal being damped further with each coupling piece and so the reception becomes worse. If there is already not a good GSM signal at the location it will be difficult to create a steady connection.

The software “FastSMSSet” hangs up or crashes, what can I do?

This indicates that the wrong Java version is being used. It is very likely that a 64-bit Java version is installed on your computer. However, the software “FastSMSSet” requires a 32-bit Java, which can be downloaded free of charge on the foolowing homepage and installed: www.java.com

How can I reset my device to the factory settings?

Remove the blue cover to reveal two buttons to the left of the SIM cardholder (Reset and Test). Push both buttons simultaneously and hold them pressed for approx. 30 seconds. The flashing pattern of the LEDs will change when the process was successful.

ATENTION: The configuration in the SMS relay is lost during this process and must be reloaded.

The “read” function is performed, however, an error is displayed during “writing”. Why?

The buffer storage of the SMS relay could be full. The device should be sent in for an inspection/repair.

How do I find our if there is something wrong with the device/SIM card/network?

  • Using the function “Diagnosis”, when the SMS relay is connected to the computer. The respective Error Code is displayed and that is described in detail in the data sheet.
  • An error diagnosis can already be established with the aid of the flashing frequency of the flashing pattern of the LEDs on the module.

What is a log file and how do I read it out of the SMS relay?

All actions are recorded and stored on the log file. This file is often required by CometReleco Support to understand what precisely is happening at the SMS relay.

This log file can be retrieved when the computer is connected to the SMS relay. A diagnosis is performed, a button with “Log file” is now visible in the newly opened window (only from FastSMSSet version 4.0.0)

How do I interpret the flashing frequency of the LEDs on the SMS relay?

– LED dark

  • module is not running


– Intermittent flashing (irregular)

  • module is starting up


– Short flashing (approx. every 3s) 1x

  • module is running, everything OK


– Short flashing (approx. every 3s) 2x

  • no credit


– Short flashing (approx. every 3s) 3x

  • time not set


– Regular flashing (every second) 1x

  • Module in  initial status


– Regular flashing (every second) 2x

  • configuration error or SIM blocked


– Regular flashing (every second) 3x

  • communication error

What is the CWS port and what can I use it for?

The CWS port www.sms-relay.com is a port used for the remote servicing of the Comat SMS relays types CMS-10F, CMS-10ADF and CMS-10ACDF. CWS stands for Comat Web Services and includes services that deal with automation via the internet.

How can I operated my SMS relay using the CWS port?

Create an account on the page www.sms-relay.com assign your SMS relay to the account. When connecting for the first time, an APN is queried, select your provider on the SIM card. Your provider is not listed? Then add it yourself manually (attention: APN data must be correct otherwise the connection can never be created).

What are the conditions to be able to use my SMS relay via the CWS port?

Supported devices: CMS-10F, CMS-10ADF and CMS-10ACDF as of firmware version 7.0.0. Notes on the firmware of your device can be found on the front os the SMS relay below the SIM cardholder. Devices with firmware older than 7.0.0 are not supported by the functions of the CWS port.

Update via CWS port does not work, why not?


  • The reception is not good enough, check the diagnosis.
  • Incorrect APN data were selected

No connection is created between CWS port and SMS relay, what can I do?

  • Check reception quality via diagnosis
  • Check APN data. These are queried the first time the module is used.
  • Password for module access in the configuration of the relay does not correspond to password in the online account. Check and change if necessary.

Relays / Contactors

How do I find the right relay for my application?

Coil voltage?

  • You can find the available coil voltages AC and DC in our catalogue. ComatReleco technical support can help you should you not find a matching coil voltage for your application.

Load to be switched?

  • Load type?
  • Is the load to be switched ohmic? Inductive? Capacity-related? This is a very important factor that must be known to be able to select the correct relay/contactor.
  • AC? DC?
  • Is the load to be switched supplied with alternating or direct current? How high is the voltage?

Switching frequency?

  • How often should the relay be switched per day, hour, minute or even second? From up to how many switching cycles is a semiconductor relay recommended, since no mechanical contact exists and so the service life is practically endless.


  • This includes e.g. the ambient temperature where the relay/contactor will be installed. Does that also include details regarding the environment: dusty? Is it damp? Aggressive gases? Other appreciable factors?

Switching small signals, what do I have to pay attention to?

  • If there are signals in the mA range then it is important to select a suitable relay with a corresponding minimum load. Here relays with gold-plated contacts are suitable. Gold has a very good conductivity. This is why small signals can be switched. However, gold tends to fuse the contacts if the currents are too high. ComatReleco also offers relays with double gold contacts. These double contacts ensure a high switching reliability for control and signal circuits.

A further possibility in addition to the mechanic relays is to use a semiconductor relay. The CSS series by ComatReleco can switch reliably already with currents from 1mA (DC) and 35mA (AC).

When do semiconductors make sense and what are the advantages?

  • For frequent and fast switching processes
  • Longlife thanks to wear-free semiconductor output
  • No moveable contacts, so bounce-free
  • Do not cause any electromagnetic interferences
  • Immune against mechanic impacts such as shock and vibration

Special relays for high inrush currents?

High inrush currents are typical for electronic ballast units, modern LED fixtures, energy-saving bulbs or power packs. These values can reach up to 250 times the nominal current. ·ComatReleco offers special relays for high inrush currents:

  • CHI14 / CHI34: Zero-cross switching up to 800A inrush current for 800us
  • C7-W10: With tungsten ballast contact, up to 500A inrush current for 2.5ms
  • C10-A15: With silver-tin oxide contact, up to 120A inrush current for 20ms
  • CIM14: Time relay with zero-cross switching up to 800A inrush current for 800us

The relay is not deenergised after the excitation voltage is switched off. What could be the cause? What can be done to remedy that?

  • The cause can be a small residual voltage in the circuit which suffices to prevent the relay coil from deenergising. The relays only require 0.1*Un to remain in an energised status! The relay would only be deenergised with a 230VAC coil when the current is <23VAC!
  • Long lines of wires/braids often cause induction voltage, which then do not permit the relays to deenergise. ComatReleco has developed a suppressor, the CEM01, to this purpose. This suppressor is connected parallel to the coil and compensates the residual current of the lines. This means that the relay can deenergise cleanly.

What effect does an RC link have when it is connected parallel to the coil of the relay?

The series connection of resistor and capacitor means that the current can die away suring the switching off process in a  damped oscillation. During the switching on process the resistor prevents the full capacitor load discharging over the switching contact. The suppressor circuit using an RC link is very well suited to alternating currents. In addition, the deenergisation is immediate.

Which control input has priority with the remanent relay?

If both control inputs of a remanent relay are on at the same time then A1 (ON) always has priority over A3 (OFF)

What effect does a free wheeling diode [flyback diode] have in a parallel circuit with the relay coil?

Free wheeling diodes protect against voltage spikes when the supply current of an inductive DC load is suddenly switched off. To this purpose the diodes are connected parallel to the inductive DC consumers, so that they are used by the supply voltage in theblocking direction. Afrer the supply current has been switched off the self-induction of the coil ensures that the current continues to flow in the original direction. Without a free wheeling diode, this would result in a voltage spike that adds to the operating voltage and could damage or destroy the switching path. However, with a free wheeling diode, the voltage spike is limited to the forward voltage of the diode (for silicon about 0.7 V). This protects the electronic components, but also the switching contacts, very effectively against voltage spikes.

Monitoring Devices

Which variables can be determined using ComatReleco monitoring modules?

Voltage, current, frequency, active power, apparent power, cos Phi, Delta Phi (phase sequence)

How can I convert an existing industrial relay into a DC current/voltage monitor?

The sockets C12B0 and CS-155 (S5-M) have a module recess, which is intended to be used for time modules/monitoring modules. So you merely require a monitoring module, which is plugable, in addition to a socket and an industrial relay. However, these current and/or voltage monitoring modules are only available for DC current!

How do I set an MRx device?

  • A description of the menu navigation etc. can be found in the device’s data sheet and the instruction leaflet.
  • You reach the menu by pressing both arrow buttons at the same time. Enter settings and you are automatically guided through the menu.

How can I measure a larger current than 5A using an MRI/MRM?

Current transformers are required to measure currents larger than 5A, which are specified in a secondary circuit with 5A. This means that high currents can also be measured, however this also means that the “scaling factor” must be adjusted in settings.

How do I connect a current transformer to MRx devices?

Wie schliesse ich einen Stromwandler an MRx Geräten an?

If you cannot find your question in the FAQ, please do not hesitate to contact us for further information.