Adding wheel/shaft speed sensors to the DL1/DL2
Disclaimer: Please note that Race Technology Ltd takes no responsibility or liability, explicit or implied, for the customer inappropriately fitting any type of sensor to a vehicle. Further, any modifications and or additions to the vehicle are done completely at the customers own risk. Any advice given by Race Technology is given on an as-is basis and is simply our opinion - it remains the customers responsibility to carry out work to a suitable standard and in a safe manner. If in doubt please get a professional to carry out the work, particularly in areas that may have safety implications.
DL1 Connector Info - DL2 Connector Info
The DL1 has 4 separate frequency inputs that can be used for wheel speeds or shaft speeds as required. In the software you are given complete freedom of what to use each input for - so there is no particular recommended use for each. Each of the inputs has a 100k pull down resistor and requires an absolute minimum of about 5v to trigger the input, no more than battery voltage (12v nominal) should be applied. The DL1 can record up to about 2kHz on it's frequency inputs based on a square wave input. If you require more than this contact firstname.lastname@example.org for instructions on how to do so. The DL1 has an internal filter to prevent excessively high frequencies being recorded, this filter requires a minimum low time of around 0.25mS to "reset" - so if the signal input is normally a low voltage and only goes high briefly when sensing a pickup on a wheel for example then the maximum frequency would be about 4KHz, alternatively if the signal is normally a high voltage but is pulled down briefly then the maximum frequency will be very low, or the signal might not be sensed at all - so this situation should be avoided.
General points on using Wheel/shaft speed sensors
There are 2 types of wheel speed sensor that can be supplied by Race Technology:
- Hall effect - This type of sensor senses a metal moving within a few millimetres of it and outputs a voltage pulse. This type of sensor is "active", i.e. it requires a voltage supply to it for it to work. The sensors supplied by Race Technology run off +5v and this can be taken from the units external voltage output. The advantages of the hall effect switches are that they are very robust and can be triggered by a moving wheel bolt (or similar), they don't require magnets attached to the wheels. The disadvantage is that they are a bit more expensive than other types.
- Reed switch - This type of sensor is really just a mechanical switch that operates with a magnet. This sensor is "passive", i.e. it doesn't require a power supply of any kind. This type of sensor is cheaper, but required that a magnet is fitted to a moving part for it to sense - so it can be more difficult to fit and test.
NOTE: It is not possible to use inductive type proximity detector switches. This type of sensor normally has an analogue output which is unsuitable for use with either the DL90, DL1 or DL2 without some additional external signal processing.
Fitting the sensor
Typically hall effect sensors are fitted to detect a moving bolt, common examples would be detecting the bolt on the back of a brake disk or on a drive-shaft. The bolt MUST pass within just 2mm of the face of the sensor - any more than this and the sensor will not work at low speeds. Also make sure that the sensor is mounted securely and cannot vibrate and touch any moving parts. If possible mount the sensor in a position that protects it from road debris that might damage it.
Route the wires from the sensor to the logger using suitable triple core wire, shielded if possible.
Using the ABS sensors already fitted to car
It is possible on some cars to use the existing ABS sensors to detect wheel speed - this should only be done on race cars where the ABS unit has been removed/disabled and if you are absolutely sure that the signals are appropriate type. Don't touch any of the ABS sensors if you are in any way unsure of what you are doing - please do not contact us for assistance in attaching to the ABS sensors, for obvious reasons we cannot advise on how to proceed.