need help find low cost SSR (relay) with 5v coil

[+grips03]

I'm trying to find a low cost SSR relay with 5v control (coil) in DPST (two form A)

 

Kind of like the an Omron G6B-2214P-US-DC5, but in SSR format.

 

SSR doesn't need to to support high current load. Current draw is minimal and voltage is either 0-5v.

 

low profile DIP / SIP format would be great

 

thanks

[+batari]

Why not use a MOSFET or two?

[Osgeld]

Why not use a MOSFET or two?

 

slightly confused though, if you need low current and the high side is 0-5 volts, with a 5 volt switch side whats the point of an SSR, they usually switch higher voltages or currents with a logical input (ie I want to switch 2 amps of 24 volts with 5 volts at practically no current off of a serial port)

 

if its low current and low voltage just use a pair of transistors like the quote above, or a pair of bjt's

 

if your interested I have some "useless" SSR's I would not mind seeing being gone, 3-8 volt input, I think 60 volt DC 80ma switching current, I think cause I never use them ... they are single pole but for cost of postage I could slip some in a envelope fer ya

 

side note I watched a guy at work cross his wiring and accidently dump 40 amps @13 volts DC though one, they make an impressive smoke generator.

Edited April 28, 2013 by Osgeld

[Andromeda Stardust]

Transistors are your friend. Mosfet or even bipolar would work. I use bipolar transistors for applications that require more juice than standard logic can apply, simply because they're cheap and easy to use. Mosfets are pretty much only useful for switching applications, but bipolar transistors can be used as digital switches or as analog amplifiers, depending on the usage. Also if you are very careful with your design, you can use a bipolar transistor to operate a higher voltage load from a lower voltage signal, for instance driving a 12V relay with 5V digital logic. You just have to be careful when mixing voltage sources in a circuit, that you design it in a way that the higher voltage doesn't bleed across to the lower side, which would damage components. Best way to approach this kind of design is a 12V power supply with a 5V regulator with common ground. The 5V regulator supplies all the logic circuits. The logic signal passes through a 10k resistor into the base of an NPN transistor. The emitter is connected to ground, and the collector to your 12V relay coil. The other side of the relay coil connects to +12V. Whenever the logic output is high, current will flow through the transistor, activating the relay. When logic is low, the transistor will not conduct. The relay can basically switch anything, but if you're just doing signal level stuff, the relay stage is unnecessary. If the load is high, you might try a lower resistor on the base to keep the transistor in the saturation region. I wouldn't use anything lower than 1k though. Most bipolar transistors are capable of outputting 100-300 times the current of current as the input, so if you are using it as a switch, you'll to keep the transistor in saturation mode at all times. So for switching operation, make sure to chose a base resistor value that will pass at least 1/100 of the maximum output load (that means in an analog circuit, you could technically use an NPN transistor to drive 10 ohm speakers from a source with a 10kohm input impedance). For switching operation, you can use the transistor to feed any load that the TTL/CMOS logic cannot handle (within the transistor's current/voltage rating, of course) even if the load requires a different voltage source from the digital logic, and basic transistors are plenty fast enough for most applications unless you are dealing with RF circuits or high-speed digital communication.

Edited April 28, 2013 by stardust4ever

[Osgeld]

it should be noted that SSR's are just prewired fets in a plastic case

Edited April 28, 2013 by Osgeld

[GroovyBee]

The logic signal passes through a 10k resistor into the base of an NPN transistor. The emitter is connected to ground, and the collector to your 12V relay coil. The other side of the relay coil connects to +12V. Whenever the logic output is high, current will flow through the transistor, activating the relay. When logic is low, the transistor will not conduct.

 

Solid State Relays do not have a coil. For coil driven relays you forgot to mention that you need to handle the back EMF generated when you de-energise the coil otherwise your circuit will most likely destroy itself on the first go.

[Andromeda Stardust]

Solid State Relays do not have a coil. For coil driven relays you forgot to mention that you need to handle the back EMF generated when you de-energise the coil otherwise your circuit will most likely destroy itself on the first go.

Crap, I forgot to mention the reverse-bias diode across the relay coil. But yeah, the textbook examples always mention to add a diode to safely discharge the relay coil to prevent damage to the circuit.

[+grips03]

Crap, I forgot to mention the reverse-bias diode across the relay coil. But yeah, the textbook examples always mention to add a diode to safely discharge the relay coil to prevent damage to the circuit.

 

I already do that

[+grips03]

Why not use a MOSFET or two?

 

Reason for relay is that I want to use Seimitsu arcade buttons (SPST) on controller for buttons 1,2,3 on Intellivision. But the Intellivision wants multiple pins sent to ground. Hence I made circuit like:

http://web.archive.o...intvsticky.html

 

This works ok, but I would like to have button 3 be button 3 and not button 1&2 = button 3. I was thinking a relay might be way to go.

 

I'm not sure how MOSFETs work, do they work like normal coil type relay and can use one button (they push button) to short multiple contacts? Namely ground and two pins.

 

I might end up using Arduino Uno for this, as I need it to decode the matrix keypad already.

Edited April 29, 2013 by grips03

[+grips03]

I got this working with logic gates.