2uk
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8ch relay 12V

Sat Nov 16, 2019 8:48 pm

I bought this product https://www.amazon.de/gp/product/B06XFG ... UTF8&psc=1 ,
in the description it was written that it is 5V and I hoped that I can use it directly without other components, I discovered after that the relays are 12V I made a complaint but I still remained with the merchandise and I do not know how to use it.
Can I put the signal from the GPIO through an ULN2803 to the relays together with a 12V source?
Image

sorry for the LED bad position
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pcmanbob
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Re: 8ch relay 12V

Sat Nov 16, 2019 9:17 pm

It very much depends upon the operating mode of the relay board.

If your diagram is correct then it would suggest you need to supply a voltage to the In pins and the board has a common ground, in which case no you can't use a uln2803 as that chip provides a ground on each output that is switched by the corisponding input.

And no ware in the linked page can I see any reference to the board operating at 5V further more the board does not apear to have a 5V regulator on board which suggests the entire board operates at 12V.

You will need to use a 2 transistor driver circuit for each input to the relay board if the above is true,
I would suggest you test the boards operation before proceeding by connecting 12V power supply to vcc and ground, then try connection 12V to an In pin and see if the relay works.
Last edited by pcmanbob on Sat Nov 16, 2019 9:27 pm, edited 1 time in total.
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2uk
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Re: 8ch relay 12V

Sat Nov 16, 2019 9:24 pm

pcmanbob wrote:
Sat Nov 16, 2019 9:17 pm
It very much depends upon the operating mode of the relay board.

If your diagram is correct then it would suggest you need to supply a voltage to the In pins and the board has a common ground, in which case no you can't use a uln2803 as that chip provides a ground on each output that is switched by the corisponding input.

Do you know if the whole board operates at 12V or just the relay coils ?
I am 60% sure that the whole board operates at 12V , when I tried to use it with a Blink program the LEDs were lit, but very weak, with 12V on "IN" und "COM" did nothing

pcmanbob
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Re: 8ch relay 12V

Sat Nov 16, 2019 9:28 pm

See above I edited my post....
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2uk
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Re: 8ch relay 12V

Sat Nov 16, 2019 11:23 pm

I did not find a 12V source but, I connected the relay directly to a 9V power supply and switched it on. After that I linked VCC and IN to (+), GND to (-) nothing happened, I linked after VCC (+) and GND and IN (-) nothing. Measuring with the multimeter I get results from COM (+) and IN (-) but I don't know what COM is
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pcmanbob
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Re: 8ch relay 12V

Sat Nov 16, 2019 11:41 pm

Ok try this.

Connect 12V supply to vcc and ground.

Connect 5V to com and the ground form the supply to IN pin

You should see the LED light up and the relay should click.

You need the 12V to actually power the relay coils.
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2uk
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Re: 8ch relay 12V

Sun Nov 17, 2019 8:17 am

pcmanbob wrote:
Sat Nov 16, 2019 11:41 pm
Ok try this.

Connect 12V supply to vcc and ground.

Connect 5V to com and the ground form the supply to IN pin

You should see the LED light up and the relay should click.

You need the 12V to actually power the relay coils.

I managed to get it to work with a 12V400mA source by connecting VCC (+) GND (-) COM (+) and IN (-) everything to 12V how to connect it so I can use it together with an ESP32 or Raspberry PI? did you say that a ULN2308 doesn't help? Inside is a step up voltage circuit

EDIT

M54562P and M54562FP are eight-circuit output-sourcingDarlington transistor arrays. The circuits are made of PNPand NPN transistors. Both the semiconductor integrated cir-cuits perform high-current driving with extremely low input-current supply. Works with the GROUND , It is good yes ?

UDN2984
UDN2982

2uk
Posts: 18
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Re: 8ch relay 12V

Sun Nov 17, 2019 9:36 am

A2982 seems to be the best solution for me, please advise me, in this case I can try to make a mini board that I will slip between the relays and use everything at 12V

pcmanbob
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Re: 8ch relay 12V

Sun Nov 17, 2019 10:13 am

If every thing works correctly the way you have it connected then you can use the ULN2803A between the pi gpio and the relay board.

connected like this

Image

you can of course use any gpio pins you want , but you must use a ULN2803A the A variant being suitable for use with the 3.3v output of the pi gpio.


Note your original diagram was incorrect , the input to R4 is connected to common and the GND from the LED is connected to the IN pin.
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2uk
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Re: 8ch relay 12V

Sun Nov 17, 2019 10:58 am

pcmanbob wrote:
Sun Nov 17, 2019 10:13 am
If every thing works correctly the way you have it connected then you can use the ULN2803A between the pi gpio and the relay board.

connected like this

Image

you can of course use any gpio pins you want , but you must use a ULN2803A the A variant being suitable for use with the 3.3v output of the pi gpio.


Note your original diagram was incorrect , the input to R4 is connected to common and the GND from the LED is connected to the IN pin.
so the COM from ULN2803A stays unconnected ?
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pcmanbob
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Re: 8ch relay 12V

Sun Nov 17, 2019 11:11 am

yes the com is only there to provide a connection for the protection diodes to the supply voltage that the ULN2803A is switching the ground to, when switching inductive loads like motors, as you are only switching a couple of LED's you don't need it.

I suggest you read the data sheet http://www.ti.com/lit/ds/symlink/uln2803a.pdf
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2uk
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Re: 8ch relay 12V

Sun Nov 17, 2019 11:37 am

pcmanbob wrote:
Sun Nov 17, 2019 11:11 am
yes the com is only there to provide a connection for the protection diodes to the supply voltage that the ULN2803A is switching the ground to, when switching inductive loads like motors, as you are only switching a couple of LED's you don't need it.

I suggest you read the data sheet http://www.ti.com/lit/ds/symlink/uln2803a.pdf

the last modification, you can correct me please where I went wrong _ I included a 3v3 regulator with a protection diode to be able to power ESP32. please tell me that everything is fine and that I can order the plate as it is designed
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pcmanbob
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Re: 8ch relay 12V

Sun Nov 17, 2019 11:43 am

Correct what ?

I gave you the circuit to connect the relay board to the pi gpio using the ULN2803A

If you want to add a esp32 arduino to the mix that's down to you, as its not required to interface the pi gpio to the relay board.
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2uk
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Re: 8ch relay 12V

Sun Nov 17, 2019 11:56 am

pcmanbob wrote:
Sun Nov 17, 2019 11:43 am
Correct what ?

I gave you the circuit to connect the relay board to the pi gpio using the ULN2803A

If you want to add a esp32 arduino to the mix that's down to you, as its not required to interface the pi gpio to the relay board.
thank you, I want to link these relays via ESP32 to the Internet and control them with Amazon Echo, PI is too big for my Project, if everything goes SUPER I will install it in the car to start the heating in the windshields and chairs in winter, to let the windows down in the summer, thank you very much for the help, if I connect IN to PI or ESP has the same function right?

pcmanbob
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Re: 8ch relay 12V

Sun Nov 17, 2019 12:06 pm

2uk wrote:
Sun Nov 17, 2019 11:56 am
if I connect IN to PI or ESP has the same function right?
I have no idea I don't use arduino's , if your project is arduino based I suggest you find an arduino forum.
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2uk
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Re: 8ch relay 12V

Sun Nov 17, 2019 12:21 pm

pcmanbob wrote:
Sun Nov 17, 2019 12:06 pm
2uk wrote:
Sun Nov 17, 2019 11:56 am
if I connect IN to PI or ESP has the same function right?
I have no idea I don't use arduino's , if your project is arduino based I suggest you find an arduino forum.
thank you

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