i am working on a source selector and i would like if possible some info to choose parts especally between normal relays or reed relays ...
Since ampers per contact is not an issue for a source selector any of the above may be used
my approach is to either use one double relay per input but i could go as well for one relay /chanel for each input to minimize crosstalk figures ...
reed relay could be very much space saving since will only consume 14DIL like a small ic
concerns around choise can be
---crosstalk in case a LR relay is used
--- influense in the signal from the coil of the relay
a) in normal relay
b) in reed relay
kind regards sakis
Since ampers per contact is not an issue for a source selector any of the above may be used
my approach is to either use one double relay per input but i could go as well for one relay /chanel for each input to minimize crosstalk figures ...
reed relay could be very much space saving since will only consume 14DIL like a small ic
concerns around choise can be
---crosstalk in case a LR relay is used
--- influense in the signal from the coil of the relay
a) in normal relay
b) in reed relay
kind regards sakis
Hi Sakis.
Reed relays are well suited for small signal since their contacts are absolutely sealed inside a glass bubble with vacuum or inerth gas inside.
They last years in very harsh (corrosive, etc) industrial environments.
Coil is very small , causes very small magnetic field and can be driven with small signal transistors (i.e. BC337) without any problem.
Reed relays are well suited for small signal since their contacts are absolutely sealed inside a glass bubble with vacuum or inerth gas inside.
They last years in very harsh (corrosive, etc) industrial environments.
Coil is very small , causes very small magnetic field and can be driven with small signal transistors (i.e. BC337) without any problem.
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correct but in a reed relay the coil is just a few mm next to the contact
is there a chance that the power that flows through the coil will also have some effect on the signal ???
Not in my experience.
They work very well with absolutely no noise issues.
I drive mine from a simple little LM1805 power supply, and I could have used the coils as a resistive load for source indicator LED's for a very elegant solution. As it was I never though about that and gave the LED's their own supply.
Shoog
They work very well with absolutely no noise issues.
I drive mine from a simple little LM1805 power supply, and I could have used the coils as a resistive load for source indicator LED's for a very elegant solution. As it was I never though about that and gave the LED's their own supply.
Shoog
If you drive your coil with DC, regardless of the distance and the power of the coil, there will be no effect on the signal after the switching moment. The theory says that only a time-variabile magnetic vector (that is changing in module or direction) can induce a voltage on a conductor immersed in the field.
So , feel safe.
I have seen manufacture specifications where they advise against operating a (normal) relay in the energised state for long periods where there is little contact current flowing. Some outgassing due to heat may cause the contacts to eventually go open circuit. Better to go for a latching relay (or a reed switch).
dc
dc
I would also endorse reed relays.
I have used hundreds/thousands of them for low level signal switching in automatic test equipment and their main benefits are:
Almost silent operation - just a very small ping!
Sealed contact envelope so no oxidation.
About 50mR contact resistance, stable over billions of operations
Although coil surrounds contact, only a few pF of capacitance, so negligible effect for audio frequencies and impedances.
Will last forever as long as high level switching of reactive loads is avoided (contact arcing). That will cause them to stick. No problem at signal levels.
I use a single reed form A relay with a 5v 10mA coil and a 0.2" x 1" footprint. This because I have a lifetime's supply in the workshop 🙂
I have used hundreds/thousands of them for low level signal switching in automatic test equipment and their main benefits are:
Almost silent operation - just a very small ping!
Sealed contact envelope so no oxidation.
About 50mR contact resistance, stable over billions of operations
Although coil surrounds contact, only a few pF of capacitance, so negligible effect for audio frequencies and impedances.
Will last forever as long as high level switching of reactive loads is avoided (contact arcing). That will cause them to stick. No problem at signal levels.
I use a single reed form A relay with a 5v 10mA coil and a 0.2" x 1" footprint. This because I have a lifetime's supply in the workshop 🙂
Why not use these:
Digi-Key - Z117-ND (Manufacturer - G6K-2P DC12)
(Note the digikey picture is wrong - the 2P package is a standard 8-pin dip.)
They are designed for small signal use.
Digi-Key - Z117-ND (Manufacturer - G6K-2P DC12)
(Note the digikey picture is wrong - the 2P package is a standard 8-pin dip.)
They are designed for small signal use.
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