Both solid state and mechanic relays electrically isolate the inputs from the outputs. Mechanical relays often need to have more power than the Propeller output pins can put out, 60ma or more and often need 12VDC to drive them as well.
The advantages of mechanical relays are that you can have more complex and complete switching with DPDT.
The big advantage of solidstate relays are that you are a solid-state device that can attach directly to the Propeller i/o.
I would've thought that, in consideration of the fact that we are talking about being directly driven by the Prop output, anything other than a zero-volt switcher (most SSR devices feature this) would be ill-advised.
Grayhill 70M-OAC is also a nice alternative that I believe I came across recently for < $10. Logic 2.5v - 10v IIRC.
The advantages of mechanical relays are that you can have more complex and complete switching with DPDT.
The big advantage of solidstate relays are that you are a solid-state device that can attach directly to the Propeller i/o.
FYI, there are solid state 3 pole relays available that can be controlled by a single prop pin. I used a Crydom 35A 3 phase relay to switch between AC line and backup power in one project. Not sure if they are also available for switching DC loads, but multiple SSRs inputs can be used parallel or series for multiple pole switching.
@Mickster
Have you ever looked at what is included in a Solid-state relay in detail?
anyways,
I tend to use mechanic relays for 110VAC as they actually are a bit physically smaller and don't require heat sinks. I like to hear the clicking as well.
Have you ever looked at what is included in a Solid-state relay in detail?
Can't say I dwelled on it, no but I used to buy them and use them (2000+/yr) until we convinced our customers to switch to DC solenoids on their hydraulic valves.
They have improved a lot since 2000+. I am not sure that means they are good in certain industrial contexts. I find that in high capacity situations they require big heat sinks that actually make them larger than conventional mechanical relays. And of course, if the heat sinks get dirty, they are no good.
They have improved a lot since 2000+. I am not sure that means they are good in certain industrial contexts. I find that in high capacity situations they require big heat sinks that actually make them larger than conventional mechanical relays. And of course, if the heat sinks get dirty, they are no good.
Ah, slight misunderstanding, sorry. The "2000+" was the quantity that I purchased each year as a machine-tool manufacturer.
I have actually been using solid-state I/O since 1981 (Teledyne) and since the late '80's, I have used the OPTO-22 standard (including Crydom, Gordos, Grayhill, Potter & Brumfield) etc., with great success.
All the above are encapsulated, sealed units and I referred to the 'M' (mini) series because they are less expensive and smaller than the hockey-puck style that the OP was looking to source from automationdirect.com.
This is the DC output version (same form-factor as the AC) that we switched to except we use the much lower cost Grayhill from Digikey:
I can't conceive of using a mechanical relay in place of an SSR here at chaos central. Just one firing of one kiln involves more than 10,000 switch closures. Considering the magnitude of the currents being switched, I doubt a mechanical relay would survive a single firing.
In contrast, an SSR, controlled directly from a 3.3V logic level, lasts a lifetime. I've never noticed the slightest indication of wear or tear after years of use. Meanwhile, the optoisolation within the SSR has provided complete protection of the logic circuitry. Groovy stuff!
I can't conceive of using a mechanical relay in place of an SSR here at chaos central. Just one firing of one kiln involves more than 10,000 switch closures. Considering the magnitude of the currents being switched, I doubt a mechanical relay would survive a single firing.
In contrast, an SSR, controlled directly from a 3.3V logic level, lasts a lifetime. I've never noticed the slightest indication of wear or tear after years of use. Meanwhile, the optoisolation within the SSR has provided complete protection of the logic circuitry. Groovy stuff!
I do have to confess to having a bias in favor of SSR's over mechanical relays in most cases, but there are times when a mechanical relay is the better choice (IMHO). Two examples are to switch off power to a motor when the E-STOP button is pressed, or when a mechanical system hits the absolute end of it's travel range.
Zetsu
Posts: 186
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http://forums.parallax.com/showthread.php?124838-Automatic-vacation-Fish-Feeder
http://forums.parallax.com/showthread.php?140126-Nice-Relays-for-1.10-ea-Prop-Potential&p=1098796&viewfull=1#post1098796
The advantages of mechanical relays are that you can have more complex and complete switching with DPDT.
The big advantage of solidstate relays are that you are a solid-state device that can attach directly to the Propeller i/o.
Grayhill 70M-OAC is also a nice alternative that I believe I came across recently for < $10. Logic 2.5v - 10v IIRC.
Mickster
FYI, there are solid state 3 pole relays available that can be controlled by a single prop pin. I used a Crydom 35A 3 phase relay to switch between AC line and backup power in one project. Not sure if they are also available for switching DC loads, but multiple SSRs inputs can be used parallel or series for multiple pole switching.
Have you ever looked at what is included in a Solid-state relay in detail?
anyways,
I tend to use mechanic relays for 110VAC as they actually are a bit physically smaller and don't require heat sinks. I like to hear the clicking as well.
Can't say I dwelled on it, no but I used to buy them and use them (2000+/yr) until we convinced our customers to switch to DC solenoids on their hydraulic valves.
Mickster
Ah, slight misunderstanding, sorry. The "2000+" was the quantity that I purchased each year as a machine-tool manufacturer.
I have actually been using solid-state I/O since 1981 (Teledyne) and since the late '80's, I have used the OPTO-22 standard (including Crydom, Gordos, Grayhill, Potter & Brumfield) etc., with great success.
All the above are encapsulated, sealed units and I referred to the 'M' (mini) series because they are less expensive and smaller than the hockey-puck style that the OP was looking to source from automationdirect.com.
This is the DC output version (same form-factor as the AC) that we switched to except we use the much lower cost Grayhill from Digikey:
Regards,
Mickster
In contrast, an SSR, controlled directly from a 3.3V logic level, lasts a lifetime. I've never noticed the slightest indication of wear or tear after years of use. Meanwhile, the optoisolation within the SSR has provided complete protection of the logic circuitry. Groovy stuff!
I do have to confess to having a bias in favor of SSR's over mechanical relays in most cases, but there are times when a mechanical relay is the better choice (IMHO). Two examples are to switch off power to a motor when the E-STOP button is pressed, or when a mechanical system hits the absolute end of it's travel range.