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What kind of relay is this?

Davewalker5

Sep 20, 2014
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What kind of relay type is this?

What tool would you guys use to get them out of the sockets

When I used pilers, it squeezed the chassis of the relay and smashed it

There is too many components around the relays to get a flat head screw driver underneath it, it lift it out
 

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Davewalker5

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How do these relay suppressor network circuits work? what do they do to the relay?
 

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Arouse1973

Adam
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What kind of relay type is thisinputs

What tool would you guys use to get them out of the sockets

When I used pilers, it squeezed the chassis of the relay and smashed it

There is too many components around the relays to get a flat head screw driver underneath it, it lift it out
Looks like a double pole single throw type. Two seperate contacts with two common Inputs.
Adam
 

Davewalker5

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I mean what type or kind of package? it's a type of relay

I'm not worried about if it's a single pole or double throw
 

Arouse1973

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How do these relay suppressor network circuits work? what do they do to the relay?

They dont do anything to the relay, they absorb the flyback energy from the coil when the relay is switched off.
Adam
 

Arouse1973

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I mean what type or kind of package? it's a type of relay

I'm not worried about if it's a single pole or double throw

I dont know I dont think relays have generic footprints like other component.
Adam
 

Davewalker5

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They dont do anything to the relay, they absorb the flyback energy from the coil when the relay is switched off.

Yes i know that is doesn't do anything to the relay

Why are each relay suppressor network circuits different, how do they absorb the flyback energy from the coil?

why didn't they just use one instead of using 3 different types which do what differently?

When the relay closes or shuts off , it creates a undershoot voltage or spike

Each Relay suppressor has a RC network configuration to time delay or to filter out the undershoot voltage spike? but why the different RC network configurations?
 

Arouse1973

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Is this a wind up? You asked what do they do to the relay?
 

Davewalker5

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Mostly when I see relay, i have only seen a Diode in parallel with the relay coil. The diode clamps the flywheel voltage. So the Diode drains and sinks the coils voltage to ground.

I don't see resistors and capacitors in different configurations like this with a relay coil. They call these networks relay suppressor network circuits

I'm not sure what the resistors or capacitors do to the relay coil

Do you?

Take a look at the 3 different types of how the resistors and caps are configured to do what to the relay coil?
 

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Arouse1973

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The first one, cap across diode limits any flyback from the diodes inductance. The second one cap and resistor is a soft suppression, this stores the flyback energy in the capacitor rather than dumping large current into the supply. This could be used for very large coils which would make the diode option exspensive. The last one I have not seen but looking at it l would think the diode across the resistor limits the power disapated in the resistor, but that just my thoughts.
Adam
 

Davewalker5

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Williamson is not me arouse1973 , i don't know who that is

The first one, cap across diode limits any flyback from the diodes inductance.

So the cap across a diode increases or decreases the diodes inductance?

what does the diodes inductance do to the flyback? or relay coil?

The second one cap and resistor is a soft suppression, this stores the flyback energy in the capacitor rather than dumping large current into the supply

What makes a hard suppression network? and what makes a soft suppression?

I'm new to suppression networks, how do u know about them?

Why would they want to store the flyback energy?

Why not just use a diode in parallel? to sink and drain off the flyback current and voltage
 

Arouse1973

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A diode clamp is very aggresive, it pushes the same current that is in the coil into the supply. This might not be allowed so caps are used to store the energy which is the slowly used by the coil until the energy is gone.
Adam
 

Davewalker5

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A diode clamp is very aggresive, it pushes the same current that is in the coil into the supply. This might not be allowed so caps are used to store the energy which is the slowly used by the coil until the energy is gone.

So you're saying that the diode sinks and drains off into the supply very fast

The cap stores the energy and sinks and drains off the flyback energy slowly back into the supply

Does the capacitor and resistor limit the "undershoot voltage"? or just the diode clamps the undershoot voltage?

Because if the flyback voltage is to large what will happen? it will damage components because it's a negative voltage spike

Semi conductors don't like a negative voltage because it breaks down the reverse biasing junctions
 

(*steve*)

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These are all methods of reducing the voltage spike which occurs when current through the coil is interrupted.

Those using diodes are for DC circuits.

Those comprising only of resistors and capacitors can also be used for AC driven coils.

A diode on its own allows the current to continue to flow around the circuit consisting of the coil and the diode until the resistance of the coil and the voltage drop of the diode cause it to fall to zero. This can make the relay slow to open, which can also cause issues with arcing contacts (because as well as a time delay, the contacts themselves open more slowly).

There are variations with zener diodes added which increase the loss in the circuit, resulting in much faster decay of the voltage. However these will allow the reverse voltage across the relay coil to rise by the zener voltage, so the switching circuit needs to be able to handle Vcc + Vz.

The variations with capacitors and resistors rely on the energy from the coil being transferred to the capacitor and dissipated in the resistor. This circuit will ring, but with luck (actually with good design) the voltage will rapidly fall below that required to hold the relay closed and subsequent rings will not be energetic enough to close (or keep closed) the relay.
 

Davewalker5

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Those using diodes are for DC circuits.

Those comprising only of resistors and capacitors can also be used for AC driven coils.

So it's an AC voltage that is charging or energizing the relay coil?

The Relay coil itself has to be an AC relay coil?

I didn't know where was DC relay coils and AC relay coils

However these will allow the reverse voltage across the relay coil to rise by the zener voltage, so the switching circuit needs to be able to handle Vcc + Vz.

What you mean by how it can handle the VCC + Vz?

The relay coil rises by the zener voltage? how can a zener diode rises the relays coil

The zener diode just "clamps" the relays coil reverse voltage
and then the zener diode sinks the relays coils reverse voltage and decays to zero
 

(*steve*)

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Firstly google flyback diode and make sure you understand it.

Then consider if you place a zener diode in series with the flyback diode so that the zener breaks down when the flyback diode is forward biased. (It's like the diode has a very high forward voltage)
 

Davewalker5

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Yes I have seen a zener diode in series, it's to protecting and stopping a negative voltage from the relay coil from entering into the circuit
 

(*steve*)

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Yes I have seen a zener diode in series, it's to protecting and stopping a negative voltage from the relay coil from entering into the circuit

  1. Do you understand what a flyback diode does?
  2. Do you understand that the voltage spike does not reverse or reduce the voltage seen by the switching device, but increases it?
 

(*steve*)

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Look at this.

It shows a transistor turning a relay on and off.

There is a switch in series with the diode. Click the switch to open or close it.

There is a graph of voltage and current shown along the bottom. This is at the collector of the transistor.

Note that when the switch is open, the peak voltage (shown in the upper left corner of the graph) is several thousand volts, When you close the switch it falls to 5.65V.

The battery voltage is 5V. Without the diode, as the transistor switches off, the voltage at the collector rises. Of course, in reality it would only rise to the point at which the transistor breaks down. With the diode, the increase in voltage is limited to the forward voltage drop of the diode (0.65V).

Once you understand this, I will add a zener diode in series with that diode to show you the effect it has.
 

Davewalker5

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With the diode, the increase in voltage is limited to the forward voltage drop of the diode (0.65V).

Right the diode Clamps/limits the relays coils voltage when the switch is turned off
 
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