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alternative to relay ?

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mic5

Member
I am using the relay to switch 230v supply to a device. A transitor gives control to the relay. I feel it is bulkY.
Is there any simple device to control the supply that operated by dc circuits?
 

BrownOut

Banned
A triac can often substitute for a relay. There are also ready-made solid-state relays on the market, which are essentially a triac with integrated driver circuitry.
 

Vizier87

Active Member
well depending on function you may opt for either the bulky or solid state ones...solid state relays are always more 'good-looking' though.
What is your application?
 

mvs sarma

Well-Known Member
I am using the relay to switch 230v supply to a device. A transitor gives control to the relay. I feel it is bulkY.
Is there any simple device to control the supply that operated by dc circuits?
A wisely chosen relay with a transistor driving it is more safe and economical even by size, compared to solid state relays. Solid state relays are more bulky and need a heat sink etc depending on the power handling capacity.
Only you need to put a snubber across relay contact. Suchan arrangement is needed in Solidstate also but may not be foolproof.
Suggest that a relay gives a stable service.
 

Leftyretro

New Member
A wisely chosen relay with a transistor driving it is more safe and economical even by size, compared to solid state relays. Solid state relays are more bulky and need a heat sink etc depending on the power handling capacity.
Only you need to put a snubber across relay contact. Suchan arrangement is needed in Solidstate also but may not be foolproof.
Suggest that a relay gives a stable service.

I agree. While most higher current rated solid state relays appear to be more compact then a similar rated relay, if you check out the data sheets you will find that to utilize any where near maximum rated current on most solid state relays requires a not so small heat sink.

The time tested relay is not to be looked down at. There are times when there are more modern components that may be better in some aspects then the lowly relay, in many cases a well specified relay is still the best/simplest/cheapest solution.

Lefty
 

zipdogso

New Member
Only you need to put a snubber across relay contact. Suchan arrangement is needed in Solidstate also
.

A snubber diode is not necessary on a solid state relay only on a mechanical one and even then only if the coil is connected to delicate equipment ie a PC or small electronic circuit.

Or at least that was as I understood it....

If in doubt use a diode certainly wont do any harm. You connect it ....Oh lord here we go ...ANTI PARALLEL across the coil connections.

And there are plenty of compact DC - AC solid state relays not necessarily cheap mind you but plenty of choice.
 
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mvs sarma

Well-Known Member
A snubber diode is not necessary on a solid state relay only on a mechanical one and even then only if the coil is connected to delicate equipment ie a PC or small electronic circuit.

Or at least that was as I understood it....

If in doubt use a diode certainly wont do any harm. You connect it ....Oh lord here we go ...ANTI PARALLEL across the coil connections.

And there are plenty of compact DC - AC solid state relays not necessarily cheap mind you but plenty of choice.

i was talking about RC snubber across the load circuit or contact of the solidstate/mechanical relays
In addition, we need a diode protection to coil in case of relay
 
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Boncuk

New Member
A snubber diode is not necessary on a solid state relay only on a mechanical one and even then only if the coil is connected to delicate equipment ie a PC or small electronic circuit.

Or at least that was as I understood it....

If in doubt use a diode certainly wont do any harm. You connect it ....Oh lord here we go ...ANTI PARALLEL across the coil connections.

And there are plenty of compact DC - AC solid state relays not necessarily cheap mind you but plenty of choice.

SSRs use VDRs instead.
 

tcmtech

Banned
Most Helpful Member
Its quite common for SSR's to be used in electrical devices now. Industrial control equipment is loaded with them.

As far as size Vs capacity I have standard issue 100 amp 600 volt rated units that even with the heat sink are still smaller than their mechanical counterparts. Plus they have the necessary snubbers and other related protection circuitry built right into them.

I have no problems or concerns with using SSR's to replace mechanical relays and solenoids when possible especially when the application requires very frequent switching of inductive loads or high in rush currents that tend to burn up mechanical contacts. Plus they dont click or bang when activated or deactivated.

Typically the good name brand devices are rather conservatively rated. I have taken apart old ones that were damaged before and found that typically the switching SCR's or triacs in them have a 2 - 4 times higher current rating than what the specs for the actual SSR device has depending upon what application they are rated for.

I have no problem using a 250 VAC 20 amp SSR to replace a mechanical relay of the same specs. Most often the actual load is far less than the peak rating and if any heat sinking is needed it small. Its quite common for SSR's to be just mounted to the nearest metal body panel with some heat sink grease between them and a set of screws.
 
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