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Topic: [partially solved] 12V relay not cooperating (mod.3393 to be used with Arduino) (Read 8908 times) previous topic - next topic

Paul__B


I decided to take a closer look at the image...


Good trick.  I could not get the images on that site to behave sufficiently to see the detail.


To activate the relay pull it to ground (not supply 3-4v) like the webpage states, place a diode in series and signal 0v to switch it on... switching it off may be an issue as it may require up to around the 12vcc input you use.


You mean to say - the information on the website is wrong?   :smiley-eek:  How could that happen?

cjdelphi


dave-in-nj


I decided to take a closer look at the image...

The 2 transistors used are S8550.   Pnp!

To activate the relay pull it to ground (not supply 3-4v) like the webpage states, place a diode in series and signal 0v to switch it on... switching it off may be an issue as it may require up to around the 12vcc input you use.


web pages states 0-4v   that was your first clue.


dave-in-nj



I decided to take a closer look at the image...


Good trick.  I could not get the images on that site to behave sufficiently to see the detail.


To activate the relay pull it to ground (not supply 3-4v) like the webpage states, place a diode in series and signal 0v to switch it on... switching it off may be an issue as it may require up to around the 12vcc input you use.


You mean to say - the information on the website is wrong?   :smiley-eek:  How could that happen?



how could we all miss that on the link to the data sheet he posted   ?

umm..... what data sheet ?

cjdelphi

The page says 0- 4v which I read yesterday... today I looked at the circuitboard


From memory I remembered 4v ... since everyone was talking about triggering an npn, so well done you got me on my memory! Congratulations. Where were you yesterday with your obvious answer

greenestmike

Uh, well, thank you everybody for taking over my topic. Just got back from office, I need to focus a little on your request(s).

First at all, trivial experiments and (mostly) read your posts made me clear that "LOW" on "LOW LEVEL TRIGGER" doesn't refer to voltage, but to the state needed to *activate* the relay. That's a fairly bad news to me, quite unused to such a mental contortion. Being on this world by long time, I should have known... :)

Now I have cleared up my previous mistake, and I managed to have the damn thing working (for the record, it's sold as 12V Arduino 2channel LOW LEVEL TRIGGER, 3393):

1) this is a 12V driven board, nothing to deal with Arduino unless by-other-means connected, see further;
2) input pin is already "pulled up" quite as Crossroads said. Should be grounded to see the relay to react;
3) to answer romanz, and after having de-soldered the relay from board, the coil hasn't burned after all and the relay is still intact. The circuit has failed somehow, but probably it's been due of powering from the "wrong" end (the coil itself). No further investigation I'll take, as there are plenty of more interesting stuff to learn on the world but still was a quite unusual happening. I'd file it under "another bad day";
4) rather than throwing everything off the window, while being the electronic waste quite regulated in northern Italy, I chose to (still) drive the damn thing using Arduino by the mean of a single PNP lying around (BC238). It works somehow BUT...

...at any give voltage provided to the base, even touching the contact with my finger, providing 5V or grounding, the relay gets crazy and turns on and off at a high speed. I suspect there's need for a pull-up/pull-down resistor somewhere, but I haven't figured out how, why and, especially, where.

(oh, schematic... shame on me, I've been spending the last HALF AN HOUR just to figure out where the ground is on the "easy" circuit editor. Imagine a PNP, have the emitter to the input pin, collector to ground and base to 5V, nothing else. Half an hour and still no go! Puah.. such a waste of time, I'd better go hunting ghosts!)


Of course, connecting Arduino thru a safety diode doesn't make the relay clicking when I expect to do.

Any clue? [sincere thanks in advance!]

greenestmike

Hello everyone and thanks for your time.
In a matter of fact I messed up with transistors while trying to use a PNP which is unfamiliar to me (being novice to the full extent of its meaning).
"My" solution, provided here for the novice(s) seeking asylum, is real simple and lies on a simple NPN BC547 with these connections:

B = 10k resistor in series to Arduino pin (say, blink on pin 13 as the example)
C = to 3393 board IN pin
E = to ground. Arduino and the board share common ground

Plus, for stability, 100k from B to ground.


Time now for a celebration :)

drksam

Why cant the board just be driven by the arduino? All you have to do is set the pin HIGH to turn it off and LOW to turn it on. I know its kinda hard to get used to but a lot of stuff works that way and its not so bad to use.
Arduino UNO, mega 2560, atmega328, attiny44, LCD, TFT, touch, SD, i2c, spi, MCP23017, android control, automation direct PLCs and drives.

cjdelphi


Why cant the board just be driven by the arduino? All you have to do is set the pin HIGH to turn it off and LOW to turn it on. I know its kinda hard to get used to but a lot of stuff works that way and its not so bad to use.


12v on the base pin.....

drksam

Arduino UNO, mega 2560, atmega328, attiny44, LCD, TFT, touch, SD, i2c, spi, MCP23017, android control, automation direct PLCs and drives.

Cactusface

Hi All,
              I don't see the problem! Power the relay board seperately as we all know to do, common ground between this and the arduino, stick any 2 arduino outputs on to the IN's on the relay board and it works, as said earlier the inverted logic that requires a input of Zero or LOW to operate the relays is a little odd, so what it works. 

If you take a look at the link to the actual item, on the bottom edge of the board, it says low logic trigger.  If you connect across the N/O contacts then 5V or HIGH will switch it ON, but the LEDS will now lie and indicate it's OFF.

Regards

Mel.
Open your mind! But not too far, your brains might fall out.
Also like Photography, model building and my 300+ Cacti and Succs.

drksam

I thought the same but cjdelphi said that it had 12 v on the base pin but iv wired a similler circuit here and I see no problems with it given I don't have these transistors but I don't see why he's reading 12 on the base pin.
Arduino UNO, mega 2560, atmega328, attiny44, LCD, TFT, touch, SD, i2c, spi, MCP23017, android control, automation direct PLCs and drives.

cjdelphi

Look...


To energize the relay, 12v is required, normally 5v relays are used with Arduino to keep arduino from seeing more than 5v.  Thisis a 12v relay, this transistor is a pnp, unlike npn where you provide > 0.7 to turn it on, pnp requires gnd, to switch it off you supply the voltage on the emitter, 12v, we can't..

But wait...

When 12v is placed on the emitter, 12v - 0.7v we end 11.3v ish volts on the base, this keeps the transistor on and the collector drivez the relay..

So how do you bring the base to ground?  If there's 11v trying to flow into the arduino? That's why I suggested a zener and shunt the excess voltage/current keeping it below 5v ... my emulator suggests it works.

Paul__B


I thought the same but cjdelphi said that it had 12 v on the base pin but iv wired a similler circuit here and I see no problems with it given I don't have these transistors but I don't see why he's reading 12 on the base pin.


Take a look at the circuit provided earlier in this discussion:
Where VCC is 12V.


drksam

I see.mmy relay board is using 24v relays and low level trigger but after studying it closer I see that my board is using MOSFETs after the transistors so sorry I was wrong my board already had that taken care of and just worked
Arduino UNO, mega 2560, atmega328, attiny44, LCD, TFT, touch, SD, i2c, spi, MCP23017, android control, automation direct PLCs and drives.

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