I'm relay just coming unswitched!

I have this application where I need a switch, or maybe more accurately, a relay. For various reasons, I thought a solid state relay would be the way to go. So, I got the one linked below. The trigger voltage is listed as 1.5 to 5 volts and the output voltage range is 0-40V with a maximum on resistance of 1.25 ohms. However, after quite a bit of testing, it's apparent to me that applying that voltage to the inputs (using the lead by the "dot" as the #1 positive lead), does not close the relay contacts on the other side. Among other tests, the resistance across the output contacts stays as an open circuit. I'm just curious if there is anyone familiar with this type of component who can tell me why it doesn't do what I thought it was supposed to do.

https://www.futureelectronics.com/e...ate-relays/Pages/8013604-AQY221R2SX.aspx?IM=0

Jim

Jim:

Pins 1 ( + )and 2 ( -) are connected to the LED. You will need a in series dropping resistor that limits forward cureent on LED. Example if you driving it with 5 volts you want a 1000 ohm or 1K resistior otherwise you will burn out LED in a short time.. If you were using 12 volts 2400 ohms or 2.4k. You are using the resistior to limit the current to suggested 5ma forward current.

The other thing you need is to have a applied load on pims 3 & 4. This is not like a mechanical relay that is closing contacts. What you have is a Optical-coupled MOS FET Here is a good FAQ on them https://www.renesas.eu/products/opto/technology/standard/index.jsp with lot more info they you may want

https://www.mouser.com/ds/2/316/aqy-sop-80v-load-catalog-462153.pdf is the Data sheet here for you part. If you need more details just shout.

Cheers
John ..

rocket1017 said:

Jim:

Pins 1 ( + )and 2 ( -) are connected to the LED. You will need a in series dropping resistor that limits forward cureent on LED. Example if you driving it with 5 volts you want a 1000 ohm or 1K resistior otherwise you will burn out LED in a short time.. If you were using 12 volts 2400 ohms or 2.4k. You are using the resistior to limit the current to suggested 5ma forward current.

The other thing you need is to have a applied load on pims 3 & 4. This is not like a mechanical relay that is closing contacts.

https://www.mouser.com/ds/2/316/aqy-sop-80v-load-catalog-462153.pdf Data sheet here. If you need more details just shout.

Cheers
John ..

Click to expand...

That makes sense on the input side. On the output side, I'm afraid I don't know what an applied load is (google isn't helping me out much). I'm trying to pass a signal through the switched part of the relay. Is there such a device?

Jim

Jim:

What i mean is on pins 3 & 4 you need to have the load like a small light bulb for example with power supply (battery) appiled to it in a complete circuit with pins 3 & 4 on the device being the switch that closes the circuit and then turns on your your light bulb. This will happen when you apply power to pins 1 & 2 as discussed before.

rocket1017 said:

Jim:

What i mean is on pins 3 & 4 you need to have the load like a small light bulb for example with power supply (battery) appiled to it in a complete circuit with pins 3 & 4 on the device being the switch that closes the circuit and then turns on your your light bulb. This will happen when you apply power to pins 1 & 2 as discussed before.

Click to expand...

OK, the resistor works on the inlet side and the switch switches (resistance across the output drops to an ohm). This might work. It'll take me a few minutes to find out.

Thanks!

Jim

Jim, if you are in need of a solid state relay for pyros or any other high current application controlled by some other voltage/current source you might want to try one of the boards I just designed. Both boards are currently in fabrication but should be done in a week or two.

PCB 1 : Pyro Amp. This board is designed to take a standard altimeter output and trigger a very large current to a motor starter. The input trigger and high current outputs are optically isolated so two batteries can be used if desired. In addition it also checks for continuity of the starter on the high current side and then mimics that continuity on the input side, this function is also optically isolated. So, the altimeter connected to this board thinks it is controlling some standard pyro starter and can even read continuity even though everything is optically isolated from the larger starter it is actually controlling.

PCB 2 : Power Controller. I designed this board as a redundant/switchless power control system for my flight computer. After designing it I realized it could be used alone for switching altimeter and pyro batteries. The board has two power inputs, altimeter battery and pyro battery. In addition it has two logic inputs, start and stop. It is basically two solid state switches with a few added perks. For instance if the input signal to start is interupted, in the case of a failed mechanical switch the unit stays on. If all power is lost due to a loose power connector an internal capacitor runs the altimeter for as long as possible until reconnected. If and when a battery is reconnected to the board it always defaults to the on position. To turn off the controller the start button must be released and the stop button must be held down for a long period of time. After the unit is shutdown it goes into a very, very low current draw off position, we are talking low micro amps.

Both boards are very small approximately 1"x1.5", all surface mount, very low mass and have standard screw terminals for connections.


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Chris, you were about to get a call from me. Who knew we were working on the roughly the same thing - you, from an organized, professional electrical engineering perspective, and me, from a somewhat different direction. In spite of my limitations, and with John's help, my little circuit works. I can take a servo in or out of service, during a flight, by switching the signal line using the output from a Raven. All I need to do now is figure out how to solder leads to something that is smaller then the legs on a tick.

My fallback was to instead switch the power leads to the servo instead of the signal lead. Sounds like your PCB 1 board would be just the ticket for that. Maybe make an extra just in case?

Jim

JimJarvis50 said:

Chris, you were about to get a call from me. Who knew we were working on the roughly the same thing - you, from an organized, professional electrical engineering perspective, and me, from a somewhat different direction. In spite of my limitations, and with John's help, my little circuit works. I can take a servo in or out of service, during a flight, by switching the signal line using the output from a Raven. All I need to do now is figure out how to solder leads to something that is smaller then the legs on a tick.

My fallback was to instead switch the power leads to the servo instead of the signal lead. Sounds like your PCB 1 board would be just the ticket for that. Maybe make an extra just in case?

Jim

Click to expand...

If you want to solder SMD components, without the matching PCB, you will probably want to do some "dead bug style" soldering. Here is an example:
[video=youtube;q53uPn1mKc0]https://www.youtube.com/watch?v=q53uPn1mKc0[/video]

Apparently, dead bug style is acceptable even for NASA, if done right. I guess, encasing it in epoxy afterwards, would be an good idea to make it more ruggedized.

There are also a bunch of equivalent parts in packages that are more friendly, like the following one:
https://www.futureelectronics.com/e...ate-relays/Pages/5026463-PVG612APBF.aspx?IM=0

Regarding servos, these are controlled by short pulses (typically 1-2ms in length, repeated every 20ms). There is a small chance, that the servo will be switched on or off during one of these pulses. In this case, the servo may twitch, after it sees a shortened pulse. This depends on the servo though, and can be easily tested by switching the servo on and off often enough to provoke this condition.

Reinhard

Another way to switch a signal like this it with a basic AND gate one input is the signal the other it's the control line. I've done this to switch 1mHz crystals with a switching circuit to make microsecond accurate timers. Logics gates typically respond much faster with less fuss

Reinhard said:

If you want to solder SMD components, without the matching PCB, you will probably want to do some "dead bug style" soldering. Here is an example:
[video=youtube;q53uPn1mKc0]https://www.youtube.com/watch?v=q53uPn1mKc0[/video]

Reinhard

Click to expand...

Hey, thanks for posting that. Interesting video.