Alan
I just went out and traced/ measured the circuits
1) I stand corrected the 12V board uses 12V relays
2) On this board the T1/D1/R2 is a separate chip (array of 8) tied to 12V bus
3) the Optocouplers output side is tied to the 5V bus (from the LM2576 chip) not the 12V Bus
4) The voltage at idle on "IN1" in your diagram is anywhere from 0 to 5V depending on how long the pin is has been open? kind of a charge build up leakage thing I would guess thing (I guess?)
5) A voltage at IN1 anywhere between about 1.35V and 3.6 v will fire the optocoupler and thus the relay. Above or below these voltages no relay action
6) R1 is 1K, r2 is I think internal to chip darlington relay driver...I can send the chip number if your really interested
In general my impression is this board is "OK" to use with the PI...your thoughts?
If I had a good CAD/schematic program , I would finish reverse engineering? and publish the schematic
Dave
NR1DX
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On 8/14/2021 10:37 AM, Alan Blind, WA9WUD wrote:
One word of caution.
The 12v board you show is probably of the optical isolation type circuit. The "input" side is an optical diode, that when set to ground, via the GPIO pin, operates the other side of the circuit, via a transistor, with its collector at 12v, where the 12v relay coil resides.
Be sure the "input" optical diode high side is no more than 5v. ? Any voltage greater than 5v, will "toast" the GPIO pin.
Since your board references a 5v power supply, it looks like that may be the case.
Here is a "typical" relay diagram
Relay.png
Alan
On Sat, Aug 14, 2021 at 9:59 AM Dave / NR1DX <manuals@... <mailto:manuals@...>> wrote:
Alan et all
That is a great find. and unlike many of the other relay boards out
there, It has actual specs, documentation and a schematic.
A bit pricey but not bad. In the end I am going to need more than 8
relays though. I looked and didn't find one by these guys. , but the
Amazooooo search engine was designed by a frustrated rat
psychologist.
They appear to be a real player in the new tech area (3D printing)
, not
just another Great Wall Knock Off shop
I? am starting with this one recommended in an earlier thread a few
months back
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But like many there is no real documentation that I could find so
far .
It takes 12V DC and has a 5V output regulator which I am guessing
could
be used to power the R-PI rather using the USB supply . My remote
antenna switch uses 12V relays
Dave
NR1DX
On 8/14/2021 6:05 AM, Alan Blind, WA9WUD wrote:
> I call that the "plate of spaghetti" phase of the project.
>
> I found these boards were very helpful in cleaning up a project.
> ?Combines a 12v to 5v power supply (RF clean), Raspberry Pi
mounting
> and eight GPIO built into the board and wired in, relays.
>
>
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>
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> Alan. WA9WUD
>
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Dave Manuals@... www.ArtekManuals.com
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