voc?
Printed From: the12volt.comForum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=138670
Printed Date: May 02, 2024 at 11:02 AM
Topic: voc?
Posted By: ircaptbob
Subject: voc?
Date Posted: March 16, 2015 at 8:03 AM
Replies:
Posted By: oldspark
Date Posted: March 16, 2015 at 8:50 AM
Posted By: ircaptbob
Date Posted: March 16, 2015 at 1:17 PM
Posted By: oldspark
Date Posted: March 16, 2015 at 6:18 PM
[ POST EDIT several hours later - retracted a statement in the last paragraph, but it's still a stupid circuit. ]
No laughs. Just the worry that a wrongly bought part can be a waste or delay etc. IMO in this case it's not wasted - it'll be handy once you start to digitise your projects...
And I'm glad you realised BEFORE connecting it to +12V!
FYI - what threw me was the "VOC". What the heck - Voltage open circuit? It's a bad silkscreen print - it should be VCC (Vcc), the common symbol for the +V supply for digital and integrated circuits. The 4 way header was then obvious - ie GND, the 2 relay actuating inputs, & and V+. I determined that In1 & In2 are GND switched from its schematic tho being intended for Arduino and similar digital projects that is the norm since digital circuits almost always use GND switching with Open Collector outputs.
The 3 pin header is a bit vague but its RY-Vcc and GND is for the relay 5V which can be a separate supply to the input supply Vcc & GND.
The jumper is there if RY-Vcc can be the same as Vcc - IOW if the optical isolation is not required. Otherwise RY-Vcc and optionally its GND can be taken to another supply source.
Not needing to connect a separate relay GND suggests the 2 header's GNDs are interconnected in which case I hope people don't move the jumper to the Vcc-GND position - that'll short out the supply! But such an interconnection defeats the purpose of the opto-isolator. Maybe further research will clarify that aspect...
But you should be able to use plain relays. I don't see that you'd need opto-isolation. Usually the desirability for such boards is the inclusion of a transistor where the trigger current is too low for the relay(s). (Having recently done a search for such boards for a friend I've been surprised by the lack of them, or rather, that they require relatively high drive currents due to the use of (BJT) transistors else use low Ohmage resistors for MOSFETs when they could be 10k and higher.)
Have a look at micro-DIN relays. They are the new common automotive relay and are half the width of traditional mini-DIN aka cube relays. And they have spade terminals which is convenient for many.
Otherwise there are many PCB mounting etc small relays to chose from.
Don't forget to match the coil voltage to your supply - eg, 12V. (Tho as in your case a 5V regulator could be used, why use an extra component along with its electrical losses?)
FYI - optical isolation the a common method of electrically isolating signals - eg, modern switchmode power supplies (SMPS) have a high voltage side (rectified 110VAC or 230VAC etc) and low voltage output (3.3V, 5V, 12V, -12V, 24V, etc). 4-pin optical photocouplers provide an electrical isolated means of communicating between the 2 supply sides.
An example of how opto-isolators should not be used is shown here - ie, no point having opto-isolation if the 2 GNDs are connected together.Not that that circuit should work anyhow - it's missing one component - and Using merely R1 (but say 1k-100k) and R3 (but 100k - 1M) and a 5V logic MOSFET (else a pull-up resistor and normal MOSFET with logic inversion of the Arduino output) is a far superior solution that places less load on the driving Arduino etc. (What a shame I left that forum... That author claims he's isolating the Arduino ouput. Silly person!)
No laughs. Just the worry that a wrongly bought part can be a waste or delay etc. IMO in this case it's not wasted - it'll be handy once you start to digitise your projects...
And I'm glad you realised BEFORE connecting it to +12V!
FYI - what threw me was the "VOC". What the heck - Voltage open circuit? It's a bad silkscreen print - it should be VCC (Vcc), the common symbol for the +V supply for digital and integrated circuits. The 4 way header was then obvious - ie GND, the 2 relay actuating inputs, & and V+. I determined that In1 & In2 are GND switched from its schematic tho being intended for Arduino and similar digital projects that is the norm since digital circuits almost always use GND switching with Open Collector outputs.
The 3 pin header is a bit vague but its RY-Vcc and GND is for the relay 5V which can be a separate supply to the input supply Vcc & GND.
The jumper is there if RY-Vcc can be the same as Vcc - IOW if the optical isolation is not required. Otherwise RY-Vcc and optionally its GND can be taken to another supply source.
Not needing to connect a separate relay GND suggests the 2 header's GNDs are interconnected in which case I hope people don't move the jumper to the Vcc-GND position - that'll short out the supply! But such an interconnection defeats the purpose of the opto-isolator. Maybe further research will clarify that aspect...
But you should be able to use plain relays. I don't see that you'd need opto-isolation. Usually the desirability for such boards is the inclusion of a transistor where the trigger current is too low for the relay(s). (Having recently done a search for such boards for a friend I've been surprised by the lack of them, or rather, that they require relatively high drive currents due to the use of (BJT) transistors else use low Ohmage resistors for MOSFETs when they could be 10k and higher.)
Have a look at micro-DIN relays. They are the new common automotive relay and are half the width of traditional mini-DIN aka cube relays. And they have spade terminals which is convenient for many.
Otherwise there are many PCB mounting etc small relays to chose from.
Don't forget to match the coil voltage to your supply - eg, 12V. (Tho as in your case a 5V regulator could be used, why use an extra component along with its electrical losses?)
FYI - optical isolation the a common method of electrically isolating signals - eg, modern switchmode power supplies (SMPS) have a high voltage side (rectified 110VAC or 230VAC etc) and low voltage output (3.3V, 5V, 12V, -12V, 24V, etc). 4-pin optical photocouplers provide an electrical isolated means of communicating between the 2 supply sides.
An example of how opto-isolators should not be used is shown here - ie, no point having opto-isolation if the 2 GNDs are connected together.
Posted By: howie ll
Date Posted: March 17, 2015 at 2:47 PM