Digital Matter does not advise connecting an immobilization relay to a safety critical system such as the ignition or fuel pump. A starter motor cut is recommended.
- The G120 has two switched ground outputs This is Pin 10 - GREEN wire, and Pin 11- YELLOW wire
- The SW GND can be wired to a relay, to control the relay
- The relay is also wired to cut/close the starter motor circuit for a vehicle, meaning that whether a vehicle is able to start or not can be controlled by the G120
- Immobilisation can be turned on/off by the G120 based on Driver ID Tag scans, or a command from the server
There are different ways to wire in a relay and configure the device settings to achieve a similar result.
However the aim is to try to avoid having the relay coil energized for an extended period of time - so as to not drain the vehicle battery if it is not driven for some time.
Automotive relays will have 2 contacts:
- Normally Open
- The 'default' state, when the relay is not energised is open (break in circuit)
- Normally Closed
- The 'default' state, when the really is not energized is closed (closed loop)
There are 2 common use cases (this guide covers case 1)
- The vehicle cannot be started until the right driver ID tag is scanned.
- In this case when the relay is not energized we want there to be a break in the start motor circuit. So we wire to the Normally Open contact.
- With this config, we can still additionally send a command from the server to immobilize the asset and prevent anyone from starting it, even if they have a valid ID. If one form of immobilization (server command or Driver ID) OR the other is active, the asset can't start.
- Default state is that the vehicle can always be started - unless via Telematics Guru or another software platform an 'immobilize' command is sent.
- In this case we want the relay when not energized to be closed, allowing the vehicle to start. So we wired to the Normally Closed contact. Sending the command will energize the relay.
Wiring and Installation
- Connect pin 86 (relay positive) to the Vehicle Positive
- Pins 30 and 87 (normally open) are wired to form the break in the start motor
- Connect the switched ground (Pin 11 - YELLOW wire) to the relay negative, pin 85.
- Any Driver ID reader of choice may be connected. See the relevant guides for these options
The DM RFID reader doesn't require any special setup. This can simply be plugged into the 4 way molex connector that comes as part of the 24 wire harness. Wiring for immobilisation will be as below
This parameter must also be set when using an iButton reader to tell the G120 to expect iButton signals.
Configure Digital Output 1
We must set that the Yellow wire is to be used for the purpose of immobilisation:
- Add the Digital Output parameter tab
- Function = Immobiliser
- Active High = No
Driver ID Parameters
The Driver ID parameter tab allows us to configure certain options based on the result of a tag scan.
- Test Against List
- This determines which tag scans are accepted as 'valid'
- If set to No - any tag scan will be accepted as valid
- If set to Yes - only a tag scan from a tag in the list on the device will be accepted.
- Buzz on No DID
- If set to YES, when a trip starts, any buzzers connected (including the internal DM RFID buzzer) will sound
- This is used to remind drivers to scan their tags when they use an asset.
- Buzzing stops once a valid tag is scanned
- If this is set to YES and Test Against List is NO - any tag scan is valid will then mean buzzing stops
- If set to Yes and Test Against List is also YES - only a scan from a tag in the list is valid and will stop the buzzing
- If set to YES - the immobiliser will be on until a valid tag is scanned.
- Once a valid tag is scanned, the asset can be started.
- Expire on Trip End
- If set to Yes, as soon as the trip ends (i.e. key off) - the scan expires and a the tag must be scanned again to restart the asset
- If set to No, it will expire after the expiry time. This is used if drivers stop for short periods during their day, and you don't want them to have to rescan every time they restart the vehicle (i.e. doing short drop offs/deliveries etc).
Configure as below for
- The buzzer to sound once a trip is started, stopping when a tag from an allowed driver is scanned
- Only a tag from an allowed driver in the list will allow the asset to be started
- As soon as the ignition is turned off (and trip ends) - a tag must be rescanned
If we set Test Against List to No, setup is complete.
Add Drivers to Driver List
Ensure a Driver List Layout is selected for the OrganisationThis should be defaulted, and therefore this step not needed, but if you experience issues check this is configured correctly.
- Admin → Organisation Manage → Edit Organisation
- Ensure a Driver List Layout is selected (Short Identifier is correct for most readers including the DM RFID reader and iButton readers)
Add Drivers to the List
Add a Single Driver
- Admin → Drivers → New
- Enter the relevant information in the dialogue shown
Add Drivers in Bulk
- Admin → Bulk Import
- Download the Bulk Import Template, fill in your driver details and then follow the bulk import process
Set which Drivers can drive each asset
We can set 'who can drive what' either on the asset, or from the driver list.
Edit asset Individually or in Bulk:
On each asset using Driver ID - make sure to check Enable Driver Management.
Choose to allow all enabled drivers in the list, or a custom list.
From Driver List:
After adding a driver, edit them and they can be set to be enabled for specific assets, all assets of a particular type.
Lists are sent down to the device about every 30 min.
If the device is tampered with, or ripped out, the relay will then default back to the "normal" position. When the asset is installed for immobilization with a valid driver ID, the wiring diagram as seen above in the article is for normally open, so if removed, the asset would not be able to start. So cutting a unit out will not allow an asset to be started.
The input monitor allows immobilization to be set based on the state of device digital inputs, i.e. immobilize on external power disconnection. Below details how to set that use case up.
The external power tab will need to be set up to a specific digital input as seen below.
Once that has been added, the input monitoring tab can be enabled so that if the specified digital input is inactive the output type actions immobilization. The digital input inactive mask will need to be set to the digital input that external power is mapped to. For example, to have the input monitor action immobilization for when the above Digital Input (10) is inactive, this would result in a binary representation of the inputs as: 10000000000 which is the decimal equivalent of 1024.
Detect Invalid Scans
Instances of rejected scans (where the tag ID was not in the valid list) can be viewed in the device logs. The below log will be captured on OEM
Driver[COM][Info]: Driver not found in list
My vehicle is immobilized and I cannot tag on
As with all debugging, this is a simple process of elimination checking all links in the chain. A few things can usually be gathered quite quickly. If the setup has been in operation for some time, and the same Tag/Device and setup is still in place, but the system stops working, we most likely have a hardware fault somewhere. For this reason it is advisable to make use of parameter templates so that we can be sure the device is using a known working set of parameter templates.
- The other scenario is the tag has been removed from the driver list.
- No confirmation beep when the tag is scanned (i.e. tag won't scan)
- Checking the Tag and Reader hardware is OK.
- Try another tag. If that one works, you have a dead tag.
- Is the LED on the driver ID on? If not, it is not getting powered. For RFID readers, with the vehicle ignition on (this wakes up the unit and has it power on the reader) wiggle the wiring on the harness in these areas
- Wires on molex plug connected to driver ID reader
- Wires on the 4 way plug on the device harness
- 4 wires connected to the 4 way plug on the device side.
- In rare cases the internal connection inside the RFID reader square box housing can come unplugged. Unscrew the housing and check all is seated.
- If the LED flickers, we have a bad connection. Replace the harness or RFID reader as necessary.
- For iButton readers the process is similar but there is less wiring and connections can be soldered so should be OK in most cases.
If the LED is on, and multiple tags won't scan (no beep) either the RFID module is faulty, or simply the buzzer (to sound the confirmation beep) is faulty. However if the rest of the set up is fine, even if the buzzer is faulty the vehicle should still start/record the driver ID to Telematics Guru. So if you are experiencing problems.
- Parameters Set Up.
- Check your parameters and wiring are correct for your application here:
- Driver ID Set Up and Immobilization
- Testing the Driver List is functioning
- If the confirmation beep sounds, but the vehicle does not mobilize, there is either an issue with the relay + wiring, device parameters or the driver list.
- The driver list may not have yet been pushed to the device. This can quickly be determined by turning off the Test Against List option in parameters, ensuring they are pushed through (pending update column clears in OEM), and retrying.
- If the tag was not in the list currently on the device - the tag will now work - as any tag scan will allow the vehicle to start.
You can check when the tag list on the device was last updated on the device by going to OEM and checking the Details page (link on left of device grid)
The time will be shown here (null in this case since no list has been sent to the device)
Telematics Guru pushes list changes to OEM every 30 minutes. After which point when the device connects in next it will get the list.
Still not working?
If a relay for immobilization is not installed - the troubleshooting process should be complete by now as you would have identified whether the tag, reader, or parameters are the issue.
However if a relay is installed, there are now 2 possible causes for the system not working
Output on device is not working.
This is quite unlikely as the FETs that drive the outputs on devices are very robust and not likely to fail. But it is possible. You should see in telemetry that the digital output is toggling off on (at least according to what the device thinks) but if there is a hardware fault, this can be tested with a multimeter.
Put one lead on the output and the other on a voltage source. When the output toggles you will get the voltage level (as the output provides a ground) and then it will drop to 0 (as it is now high impedance)
Relay is faulty
12V relays typically work fine in 24V systems for a while, but then they burn out early. In this case even though the correct inputs are being applied on the relay control, it won't toggle to allow the vehicle to be started. In this case change the relay.