ABS Relays
In order to determine the condition and quality of a relay in its dynamic mode we
must use an oscilloscope.
The circuit is the control circuit as it receives the 12v to the windings the magnetic
field starts to build up and switches the relay. As this switches the power circuit
switches on to give 12v power. The control circuit contact bounces which is where the
control circuit gets the small 12v back and the power circuit loses its voltage for a split
second.
Connected: Channel 1 to point 30 white
Channel 2 to point 87 white and green
Coils of relays K38, K100 Activated from ECU pin1 in same time, but for activating
solenoids by relay K38, current goes through the relay K39.
Relay K100
Connected: Channel 1 to point 85 grey and green
Channel 2 to point 30 red and yellow
Trigger signal from pin 28 (through transistor) by ECU, activated coil in relay K100, closed contacts and current goes through the relay to a motor pump.
Point (1) is the solenoid switched off. Point (2) pump relay switches on. Point 3 shows voltage pulled down pump is switched on. Point (4) is pump interference.
By applying a pulsating current through the coil, we open and close the contacts of the
relay so that we can observe using oscilloscope the starting point and time that it takes
for the relay contacts to open and close therefore determining the quality of the relay itself.
Relay K39
Connected: Channel 1 to point 30 white and green
Channel 2 to point 31 brown and yellow
The coil in relay K39 activated by ignition key.
Pick voltage in the coil, does occur closed contacts in a relay
The less interference we get from measuring the above data, the better the quality of relay itself (relay K38 and K100).
As we observe, stronger interference in data indicates degraded relay (K39).
I recommend replaced relay K39.
If the contacts are passing a load current of say 10A, then the voltage drop across the contacts is 0.2 x 10 = 2 volts. As the contact tips begin to wear, and if they are not properly protected from high inductive or capacitive loads, they will start to show signs of arcing damage as the circuit current still wants to flow as the contacts open. This arcing or sparking will cause the contact resistance of the tips to increase as the contact tips become damaged. If allowed to continue the contact tips may become so burnt and damaged to the point were they are physically closed but do not pass any or very little current.
If this arcing damage becomes to severe the contacts will eventually "weld" together producing a short circuit condition and possible damage to the circuit they are controlling. If now the contact resistance has increased due to arcing to say 1Ω's the volt drop across the contacts for the same load current increases to 1 x 10 = 10 volts dc. This high voltage drop across the contacts may be unacceptable for the load circuit especially if operating at 12 or even 24 volts, then the faulty relay will have to be replaced.
Channel 1, Earth and pin 1B. Solenoids.
how the solenoids start to work, under different pressure.
What about solenoids? A solenoid is another form of electromagnet. It is an electromagnetic tube generally used to move a piece of metal linearly. Solenoids are used in all sorts of places, especially locks. If your car has power locks, they may operate using a solenoid. Another common thing to do with a solenoid is to replace the nail with a thin, cylindrical permanent magnet. Then you can move the magnet in and out by changing the direction of the magnetic field in the solenoid.
How do I know there's really a magnetic field? You can look at a wire's magnetic field using iron filings. Buy some iron filings, or find your own iron filings by running a magnet through playground or beach sand. Put a light dusting of filings on a sheet of paper and place the paper over a magnet. Tap the paper lightly and the filings will align with the magnetic field, letting you see its shape!
Motor pump wave form
The motor pump relay closed and opened circuit, from positive side of motor pump.Relays are simple electromechanical switches that operate on electromagnetic principles. Each relay contains a few simple parts that all work together to allow the relay to function. Each relay contains an electromagnet, which controls the opening and closing of the relay, and an armature that actually opens and closes. Relays also contain a spring, which forces the relay back to its original state after each cycle, and a set of electrical contacts to transfer power. Relays are used most often when it's necessary to switch from a small amount of power to a larger amount, and they are used to efficiently regulate the flow of energy in an application. Relays also can be placed in tandem, in order to "step up" to very high voltages.
How a Relay Works.
A relay is made up of two circuits. One circuit is the switch, which controls power to the electromagnet that controls the relay. With the electromagnet turned on, the armature is attracted to the contact point, and upon contact the armature completes the circuit. The completed circuit allows the current to flow freely, activating whatever device the relay is designed to operate. When the first switch is turned off, the electromagnet loses power and stops attracting the armature. The spring pulls the armature away, and it is released from the contact point, and the second circuit opens. This is most easily seen in a light switch. Flip the switch, and the light comes on; flip it the other way, and you have darkness.
Electrical relays are devices which provide an electrical connection between two or more points. An electrical relay is activated when some sort of switch or other control signal is activated. Essentially, electrical relays control the flow of electricity within an electrical system. Many types of electrical relays exist.
Electromechanical Relays
Electromechanical relays, or EMRs, are the most common type of electrical relay. They come in a wide variety of shapes and sizes, but essentially constitute an electrical switch. Electromechanical relays function by applying an electrical control signal which causes a magnetic flux. This magnetic flux becomes a pulling force which operates all the electrical contacts within the relay. The contacts are what actually control the flow of electricity through the relay.
Electronic Relays.
Electronic relays are a different type of electrical relay which use a transistor or some other type of electrical switch as the main switching element in the relay.
One of the more important parts of any relay is the coil. This converts electrical current into an electromagnetic flux which is used to operate the relays contacts. The main problem with relay coils is that they are "highly inductive loads" as they are made from coils of wire. Any coil of wire has an impedance value made up of Resistance R and Inductance L in series . As the current flows through the coil a self induced magnetic field is generated around it. When the current in the coil is turned "OFF", a large back Electromotive Force voltage is produced as the magnetic flux collapses within the coil . This induced reverse voltage value may be very high in comparison to the switching voltage, and may damage any semiconductor device such as a transistor, FET or microcontroller connected to the coil and used to control the relay.
