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What are Relays used for

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walters

Banned
What are Relays used for?

I seen Relays used for Switching inputs , outputs, grounds

The relays used to Isolate the grounds how do design engineers do this?
 

Phasor

Member
I'm not quite sure what your current understanding of relays is... but in general, relays are either used for

1 - Switching a higher power load, than what the control circuit can supply.

or

2 - Providing electrical isolation between a control circuit and the switched load.
 

Sebi

Active Member
The polarized relay contain a magnet, without current give no contact.
When the coil energized with DC, one contact close, with opposite polarity
close another contact.
This relay commonly used many years ago in teletype (telex) machines.
 

eblc1388

Active Member
Sebi said:
The polarized relay contain a magnet, without current give no contact.
This would be an exception rather than the norm.

Most polarised relays I found on the NET would held the contact in either states until changes by applying a reversing flux.
 

bloki

Member
an electrical device which is activated by a current in one circuit to open or close another circuit.
a device to receive, reinforce, and retransmit a signal.
 

walters

Banned
I seen this Design tech. take a regular preamp and eq circuit before it had no relays and then he added like 40 or more relays to do all the switching,grounding,isolation

How do you use relays to do isolation?
i think he used relays like isolation transformer

How do you use relays to isolate the ground from circuit ground from
The lighting panel grounds to run lights from the relays them self have to have another grounding so you don't hear the clicky cheater coming up from the ground

I know to use a isolation transformer to with alot of secordary isolation
terminal to use it to seperate all the grounds

How do most most design tech modify a circuit that has No relays and
then adds alot of relays to do all the switching,grounding,isolation?

The switch on the front panel would be a DC voltage going to the relay?
and the relay would handle all the switching,grounding,isolation?
 

Sebi

Active Member
eblc1388 said:
Sebi said:
The polarized relay contain a magnet, without current give no contact.
This would be an exception rather than the norm.

Most polarised relays I found on the NET would held the contact in either states until changes by applying a reversing flux.
Yes, today the original polarised relays not used.
I also know the relays as You described: i think this also called as "remanent-flux" or "adhesive" relay...
Sometimes the name depend from country :eek:
 

Thunderchild

New Member
may i ask the obvious... what do u want to do with a relay do u actually understand what it is ? if u take a standard relay and open it up (recomend a large one for ease) u will probably get a good idea of how it works. it seems to me that u just like relays and complication and want to know how to add a bunch of relays: perhaps the technician u refered to used the relays to create a sort of switch box for multiple audio inputs to the same preamp/equalizier. he could possibly done this (depending on the situation and isolaton requirments) done the same with ICs but relays can be more easily treated as mechanical switchs as that is what they r just that they are not flicked with the hand but by an electromagnet so they r electricaly controlled switchs
 

walters

Banned
I know he re-designed my friends preamps and eq's , the designer
Wraped relays around the whole preamp circuit to cut down on the wires to the front panel and did isolations, ground isolations, inputs and outputs , voltages the each relay did all this

How can i take a basic preamp circuit and wrap the basic circuit with
a bunch of relays to handles all the grounding, isolations, inputs and outputs and voltages ?
 

Thunderchild

New Member
well as for cutting down on the wireing on the signals and hence interferance problems yes. two switch between two stereo signals a 6 or 9 (if u want to switch the GND as well but it is not always necesary) pin switchs r needed so if all this was led to a control pannel and back again then yes the rela reduced the wiring as it is activated with just two wire the power to the coil switching it on and off and controlling the complicated wireing at a distance rather than taking all the wireing to the control pannel. u r however not being that specific on what u want to do with a relay and do ur self a favour: do not do something thAT IS UNECESARY AS MORE COMPLICATED IT IS THE MORE DIFFICULT IT IS TO SOLVE A PROBLEM
 

walters

Banned
Thanks for the information

a control pannel and back again then yes the relay reduced the wiring

How do i reduce the wiring on the control pannel ?

If i have a control panel with a bunch of wires and alot of switches how can i use relays to reduce the wiring and switches on the control panel?
 

Thunderchild

New Member
it depends on where the wires come and go from. forexample if there is an input output paneland say u have two inputs being switched to one output and the in/out sockets are close together and the control apnnnels is a little distance away (this could be even like meters in some aplications) the the relay in the vicinity of the sockets and just the relay on off wire to the distant pannel will reduce the wiring it just depends on the situation
 

walters

Banned
A relay gets turn on and off by a Voltage ?

So on the front control panel all the switches are just Relay voltage input switches to turn on and off the relays ?

I know the designer had the Relays Turn off certain parts of the circuit
that was not being used at that time to cut down on the Noise and make the preamp or eq's filter circuit more quiet

A Relay is a Voltage controlled switch ?
you send a pulse or voltage to the trigger input of the relay and it does the switching for you
 

Thunderchild

New Member
a relay is turned on just like any otherm thing (light bulb ?) u just supply it the required voltage that normally is printed on the relay they can operate from 3 to 24 volts so get the ones best suited to ur application. when the relay is off the contacts of the switch will be on one side and when it is on it will switch to the other side (a comutator) so it is an electrically controoled switch. remember that relays DO use current from 50 mA to even 1A for the ones with high amperage switchs and some have 3 comutators in one although 2 is more common as r thjose with one. of course the more the more expensive they r (yes do not underestimate that) if u need to totaly isolate a stereo signal with the ground as well then u need three comutators. check the prices as it may be cheaper to use say two double comutators (u could even treat the L and R GNDs seperately then) with most relays the switch off when the power ceases but some (like tose used in house switching circuits where any number of switches control one light) have a mecanism in them so that just a pulse in necesary to change the commutators but these r of course more expensive and less common however they will use less powr as they only need a momentary pulse to switch and so will last long as they are not always on so may be worth it in some cases but they may be difficult to obtaoin and do cost more
 

walters

Banned
How does a Relay reduce wires to the control panel all the wires have to go to the relays on the circuit PC board so only running One wire to the front panel switch to the relay and the relay on the PC board handles all the wires and traces and switching
 

Thunderchild

New Member
if the control pannel is some distance (and the wires to be switched r close together) then the relay is place near the wires and the relay control on the pannels in this way instead of taking 6-9 wires to the control pannel only the two necesary to power the realy are run and if there are a number of relays a common negative can be used meaning 1 wire per relay and up to 1/9th of control pannel to pcb wiring
 

walters

Banned
Yea i just saw one or 2 wires from each switch going to the relays
on the PC board and the relays on the PC handled all the grounding,isolations,turning off some of the circuits, inputs and outputs

BEfore this relay modification or relay up grade there was alot of wires
about 30 or more wires going to the front control panel to the switches

Now the Switches just have the power voltages wire to the relays to turn them on and off
 
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