Replacing a relay with a switch

Thread Starter

Zeno53

Joined Sep 23, 2020
60
I need to be able to select the signal from the output of two different opamps and I need a selector. I would not like to use a relay. I have seen that there are type of switches that when powered, exchange the contact. Have you ever used them? Something like ss-relays but with deviation. It must drive 5Volt max 100mA in RF.

Thank you
 

AnalogKid

Joined Aug 1, 2013
9,256
1. What are your reasons for not wanting to use a relay?

2. A powered device that exchanges contacts sure sounds like a relay to me. Can you give a better description of a photo or a link? For example, what do you mean by "exchange the contact"?

ak
 

Tonyr1084

Joined Sep 24, 2015
5,976
This is a relay:
1622302899197.png
This is a switch and its schematic representation:
1622302928656.png1622302954492.png
A relay is just that - it relays commands. When you command it to be "ON" then it switches contacts from NC to NO, closing the NO contacts with the C (common) contact. The above relay is a DPDT relay, the switch is just a SPDT switch.
 

Reloadron

Joined Jan 15, 2015
5,934
You mention RF so what frequency are you switching? With 5 volts 100 mA you are looking at low power but any switch depending on frequency of your RF is going to have some loss. Again, exactly what frequency(s) are you switching?

Ron
 

Jim@HiTek

Joined Jul 30, 2017
18
How 'bout using a 74HC4066? The spec'ed -3db bandwidth is 200 MHz. Runs at 5V. Wait, needs to pass 100mA?....Hmmm. Nah, has 95 ohms resistance so wouldn't do good for passing 100mA. Never mind.
 
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Yeah and with that so goes the cost.
Then for those into relays, there is the notion of live or not live feeds. Some relays have to have no signal to switch.
Some of the RF switches used for cable boxes are of the magnetic latching type.
Then there is me when I used mercury wetted relays to switch low currents and relays that can switch 40 kV at 3 amps or so, but they have to have no signal when switching. I have no idea where I learned all of this stuff. It wasn't school. It's probably more like, you have an application, so you talk to an application engineer.

It was fun doing measurements at the picoamp region one day and 3000 Amps on another.
 

Yaakov

Joined Jan 27, 2019
3,155
I need to be able to select the signal from the output of two different opamps and I need a selector. I would not like to use a relay. I have seen that there are type of switches that when powered, exchange the contact. Have you ever used them? Something like ss-relays but with deviation. It must drive 5Volt max 100mA in RF.

Thank you
"RF" Isn't a specification. What frequency and bandwidth? What, precisely is your objection to a relay?
 

Thread Starter

Zeno53

Joined Sep 23, 2020
60
This is a relay:
View attachment 239920
This is a switch and its schematic representation:
View attachment 239921View attachment 239922
A relay is just that - it relays commands. When you command it to be "ON" then it switches contacts from NC to NO, closing the NO contacts with the C (common) contact. The above relay is a DPDT relay, the switch is just a SPDT switch.
I have two signals which will be one on NC and the other on NO then I will select them by activating the switch on the IC and the signal will come out on C. The reason why I chose a switch on ic instead of a physical switch is that I want to avoid lengthening the signal path. So with the physical switch I exchange the signal on the IC. In any case I want to use a switch without a solenoid as the relay coil.
 

Reloadron

Joined Jan 15, 2015
5,934
I have two signals which will be one on NC and the other on NO then I will select them by activating the switch on the IC and the signal will come out on C. The reason why I chose a switch on ic instead of a physical switch is that I want to avoid lengthening the signal path. So with the physical switch I exchange the signal on the IC. In any case I want to use a switch without a solenoid as the relay coil.
Well and fine but you still have no mention of frequency since you called out RF? There are dozens of SPDT RF switches to be had out there. Without knowing a frequency it's rather hard to suggest one. A simple Google of RF Switches will bring you up a few dozen switches so choose the one you want. I am done with asking questions which go unanswered.

Ron
 

anniel747

Joined Oct 18, 2020
1,063
I have two signals which will be one on NC and the other on NO then I will select them by activating the switch on the IC and the signal will come out on C. The reason why I chose a switch on ic instead of a physical switch is that I want to avoid lengthening the signal path. So with the physical switch I exchange the signal on the IC. In any case I want to use a switch without a solenoid as the relay coil.
Why would a switch lengthen the signal path?
 

Tonyr1084

Joined Sep 24, 2015
5,976
The reason why I chose a switch on ic instead of a physical switch is that I want to avoid lengthening the signal path.
So - depending on the frequency (RF stands for Radio Frequency) - you want a transistor or MOSFET arrangement of some sort. The devil is in the details, and the devil, along with the details, is hiding.

They say the dumbest question is the one nobody asked. Meaning even a dumb question is better than no question at all. And so it goes with the dumbest answers as well. The dumbest ANSWER is the one nobody answered. It is better to give a dumb answer than to give no answer at all.

So you want to switch RF. OK. I'll assume you want to switch an RF value of 20 hertz. Not exactly a true radio frequency, but nevertheless, the solution to 20Hz is vastly different to a frequency of 20,000,000 (20 Mega Hertz). And the way you switch them is critical to know as well. Using a DC source to control the switch? Using an AC source to control the switch? Details. All necessary information. Otherwise we're trying to decide what color to pain the car when we don't even know IF it's a car, truck, boat, plane or space ship.

Please understand our frustration. If we ask a question and you don't know the answer - just say "I don't know." There's no shame in not knowing something. There's LOTS of things I don't know. There's lots MORE things I don't know I don't know. It's smarter to say "I don't know" than it is to try and give an answer that may have nothing to do with anything real or imagined. So start over. Give us ALL the details we've been asking for. Then we can begin to help you. But if you just want a switch - Lowe's and Home Depot have a whole bunch of them.
 
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