Arduino - Digital AC control system for '80 911

[Rawknees'Turbo]

Originally Posted by Discseven

Formally, the proboscis vent. Rono, know you're thinking in an alternative vein.

Originally Posted by Discseven

Speaking of fracking, I bet that little chap is having probiscus thoughts, too !!!

[Discseven]

Originally Posted by kuehl

Karl,

I don't know squat about electrons, negative runs to positive.

I'm guessing 200 might mean up to 200k ohms and 2000 might mean 2000 ohms ?

Most meters, read 0 (zero) when you have the unit set to continuity, ohms or resistance.
and you are only touching its 2 probes together, (keep your friggin fingers off the contacts).


Anyway... Let's get out the User's Manual.

Am not asking you how to operate multi CG---I read manual! Am asking you for S&G's what ramifications of 0.3 ohms is relative to that section of wire's responsibility within AC system?

PS - my fingers were on contacts/probes. Does that mean do-over? (I admire your detailedness.) BTW, went to your site and read through your troubleshooting section. Impressive coverage.

[Rawknees'Turbo]

Originally Posted by Discseven

. . . my fingers were on . . . probes . . .

Yer a naughty man, Karlicous - love it!

[Discseven]

Originally Posted by Rawknees'Turbo

Speaking of fracking, I bet that little chap is having probiscus thoughts, too !!!

"Probiscus thoughts" ....LMFAO Rono!

Not sure if you did that intentionally or not but it's dammfunny (to my simple mind.)

[Rawknees'Turbo]

^^^

100% intentional, word Tomfoolery on my part, Karl - ha ha!

[kuehl]

Dearest Uncle Karl,
Again, my apologies. I'm simply never politically correct on Mondays.
I should have sat on the PARP.

So, your question is, assuming "I" am reading your new meter correctly.
Is a value noted a realistic value in the cases of:
1 = Probes touching, . 7 ohms = NO, should be 0
2 = Probes + extension wire, .9 ohms = Probably NO, but once you get "1" above to read 0, then measure the extension by it self and do the math.
3 = Probes + extension + green wire from T-switch back to power wire at compressor, 1.2 ohms = Probably NO, until you resolve "1" and "2".

There are:
Known knowns
Unknown knowns
Known unknowns, and
Unknown unknows.

[Rawknees'Turbo]

^^^

Looks like a lot of touching and probing required to get the job done; I'm sure Uncle Karl is up to the task!!!

[Discseven]

Originally Posted by Rawknees'Turbo

^^^

100% intentional, word Tomfoolery on my part, Karl - ha ha!

CircuscircusBro!

Originally Posted by kuehl

Dearest Uncle Karl,
Again, my apologies. I'm simply never politically correct on Mondays.
I should have sat on the PARP.

So, your question is, assuming "I" am reading your new meter correctly.
Is a value noted a realistic value in the cases of:
1 = Probes touching, . 7 ohms = NO, should be 0
2 = Probes + extension wire, .9 ohms = Probably NO, but once you get "1" above to read 0, then measure the extension by it self and do the math.
3 = Probes + extension + green wire from T-switch back to power wire at compressor, 1.2 ohms = Probably NO, until you resolve "1" and "2".

There are:
Known knowns
Unknown knowns
Known unknowns, and
Unknown unknows.

My upgraded multi is... instantly downgraded. It has NO tare. (I now realize some do.) Not sure if that is what you're suggesting for "0" value on connected probes. (Could tare both probe + extension.)

Will test again----without touching probes.

Unknowns are food for thought.

[Discseven]

Originally Posted by kuehl

Dearest Uncle Karl,
Again, my apologies. I'm simply never politically correct on Mondays.
I should have sat on the PARP.

So, your question is, assuming "I" am reading your new meter correctly.
Is a value noted a realistic value in the cases of:
1 = Probes touching, . 7 ohms = NO, should be 0
2 = Probes + extension wire, .9 ohms = Probably NO, but once you get "1" above to read 0, then measure the extension by it self and do the math.
3 = Probes + extension + green wire from T-switch back to power wire at compressor, 1.2 ohms = Probably NO, until you resolve "1" and "2".
[/I]

2nd resistance test - Checked meter with 2.7 and 220 ohm resistors to sort out dial settings and confirm meter working. (Was not set correctly for 1st test.) After testing resistors, tested:

1. Probes
2. Probes + extension wire
3. Probes + extension wire + green wire from cabin to power at compressor... and never touching probes.

O resistance for all. Given the 2.7 and 220 resistor tests proofing meter working to spec, green wire reading has to be correct. Is it possible there's zero resistance?

[RDM]

Originally Posted by Discseven

Is it possible there's zero resistance?

Within rounding error, yes. That's what I'd expect. It's not actually zero resistance, but it's lower than your meter can measure. I think that means you're good.

Since you asked, I have enjoyed reading your thread from the beginning, much less the PARF-ness lately. China- fine. We can all participate in that. I don't consider this forum to be one dimensional without politics injected. In fact, without the politics, many other things can bloom. Like friendship. Since you asked.

[kuehl]

Karl,

Assuming a 12 awg wire, figure 0.016 ohms nominal for 12 ft run.
If you read the owners manual for the meter it might tell
you the rounding is to 1; exclusive of the accuracy of the meter,
room temperature, etc. PARF!

[Discseven]

Originally Posted by RDM

Within rounding error, yes. That's what I'd expect. It's not actually zero resistance, but it's lower than your meter can measure. I think that means you're good.

Since you asked, I have enjoyed reading your thread from the beginning, much less the PARF-ness lately. China- fine. We can all participate in that. I don't consider this forum to be one dimensional without politics injected. In fact, without the politics, many other things can bloom. Like friendship. Since you asked.

Dru... appreciate input including personal commentary. Always enlightening to gain opinions... on PARF-n-all... Danke. A hoist to friendship far and wide

Originally Posted by kuehl

Karl,

Assuming a 12 awg wire, figure 0.016 ohms nominal for 12 ft run.
If you read the owners manual for the meter it might tell
you the rounding is to 1; exclusive of the accuracy of the meter,
room temperature, etc. PARF!

TY UncleCharlie. PARF!

Technical. Relay #2 is in hand. Tomorrow's agenda = wire it up and see if round 2 goes better than 1st. Is possible I put too much heat on pins when soldering... and fried components. Will do differently this time. Plan is to "bench" system in car. If relay works, will move on to finish install. John suggested a test which I now also have a 2nd step down for---plan being to always keep Arduino's power isolated from power served to relay's coil.

[RDM]

Karl,

Today is a good day, as four elements were officially named AND UNESCO has recognized Belgian beer culture as a treasure of humanity. This one's for you!

[Discseven]

^^^ HA! That's impressive! TY for the hoist/one Dru!

Relay #2. Is same as 1st. Comes with (blue) jumper that de-isolates relay’s coil power from Arduino. Will remove jumper and serve 2 isolated power supplies to relay. On signal side goes Arduino power. On coil side am going to test 12v stepped down to 5v 3amp served from car's fuse panel. Ground on both sides is common.




Different approach this time. No soldering/heat.




New step down for 5v test. Intentionally got this so preferred gauge wires can be attached. Using 16 gauge on 12v side. 26 on 5v. Will “bench” in car tomorrow morning.

[Discseven]

2nd relay - Not working either. This time heat is not a potential culprit. Power is feeding coil side and I confirmed (via YouTube for this relay) that 5v works this coil. (Last relay 12v was going to coil.) Power is going HIGH and LOW to signal pin---I checked the pin to confirm when: When relay’s LED light is ON, power signal is LOW. When light is OFF, power signal is HIGH. (That seems opposite to me but doesn’t matter at this stage.) What matters is the normally closed side which has continuity to the common… that continuity never changes regardless of the relay signal being HIGH or LOW / light ON or OFF. I tapped on the relay to possibly free a stuck coil contact but that did nothing. I also tested both relay switches (as this is a dual config)---same results for both.

If relay has power to the coil---and it does, and the signal is changing---it is as I measured & confirmed at the signal pin... continuity with the common should change between the relay’s normally closed and normally open terminals. That’s not happening. Fact that both the 1st and 2nd relays are behaving the same… finger’s pointing to human error. What have I got wrong here? There’s power offered to operate the coil and the signal is shifting and no relay magic…

Seems I’ve tested everything but have I?

Electrical expertise is most welcome.

[Jonny H]

^ I'll have a stab and say that the digital output that is connected to the relay board opto coupler needs its configuration set to 'open drain'.

What happens when you ground IN2?

[fitchn]

Discseven,

Few things.

It's pretty typical for these types of relay modules to be active low, meaning the high-current side of the relay conducts when the digital control line input is 0V (low), and doesn't conduct when the control line is 5V (high). The LED indicator lights up when the relay should be in conduction mode, i.e. the input is 0V, which agrees with your observations. You can understand that by looking at a typical schematic, like this one:



So, reading from the schematic, an input logic low (0V) turns on the indicator LED and simultaneously the LED in the opto-isolator. Under these conditions, the isolated NPN transistor turns on (conducts), which drives the base of Q1, turning it on as well, and conducting current through the low-current side of the relay, which in turn switches it into the conducting position. With an input logic high (5V), the indicator is off, so is the opto-isolator, and so is Q1.

With all that in mind, there are a few potential errors with your hardware/wiring setup. (1) you may need to connect both ground signals or at least confirm that they are connected on the module itself. One is certainly on the optically-isolated side (emitter of Q1), but without a schematic for your module I'm not sure where the other one goes. (2) Are you sure the module can be powered (JD-VCC) off 5V? The datasheet for your relay indicates the coil activation current is 30mA and the coil resistance is 400 ohms. With 5V, you're only driving 12.5mA (max, that ignores the voltage drop across Q1 which in saturation is probably 0.5V or so), which probably isn't enough to activate the relay. THIS IS MOST LIKELY YOUR PROBLEM.

Best, Noah.

[Discseven]

Originally Posted by Jonny H

^ I'll have a stab and say that the digital output that is connected to the relay board opto coupler needs its configuration set to 'open drain'.

What happens when you ground IN2?

Thanks Jonny... When you refer to "the digital output," are you saying that the Arduino's sketch/program needs to specify "open drain?"

Will test grounding IN2 tomorrow morning and post.

Originally Posted by fitchn

Discseven,

Few things.

It's pretty typical for these types of relay modules to be active low, meaning the high-current side of the relay conducts when the digital control line input is 0V (low), and doesn't conduct when the control line is 5V (high). The LED indicator lights up when the relay should be in conduction mode, i.e. the input is 0V, which agrees with your observations. You can understand that by looking at a typical schematic, like this one:



So, reading from the schematic, an input logic low (0V) turns on the indicator LED and simultaneously the LED in the opto-isolator. Under these conditions, the isolated NPN transistor turns on (conducts), which drives the base of Q1, turning it on as well, and conducting current through the low-current side of the relay, which in turn switches it into the conducting position. With an input logic high (5V), the indicator is off, so is the opto-isolator, and so is Q1.

With all that in mind, there are a few potential errors with your hardware/wiring setup. (1) you may need to connect both ground signals or at least confirm that they are connected on the module itself. One is certainly on the optically-isolated side (emitter of Q1), but without a schematic for your module I'm not sure where the other one goes. (2) Are you sure the module can be powered (JD-VCC) off 5V? The datasheet for your relay indicates the coil activation current is 30mA and the coil resistance is 400 ohms. With 5V, you're only driving 12.5mA (max, that ignores the voltage drop across Q1 which in saturation is probably 0.5V or so), which probably isn't enough to activate the relay. THIS IS MOST LIKELY YOUR PROBLEM.

Best, Noah.

Appreciate input Noah... 1) I did confirm the ground on both sides on the 1st relay having continuity. I believe 2nd matching relay does same but will confirm tomorrow. 2) "Sure" as you mention it is questionable. I checked multiple references online and there are indications that 5v works the coil in this particular relay. 12v was also tried in the first relay. Given the variables, I hold we cannot be "sure" until whatever the issue is here is discovered.

Found a fellow on YouTube with same problem concerning relay not triggering. Link below is fellow's 4th vid on subject. When he connects 5v to relay... it switches. He initially thinks it's a current issue.

https://www.youtube.com/watch?v=ozYRj-wuRNs

Same guy, different link... it's a code issue. He's missing: pinMode(1, OUTPUT) But, he's not driving his relay with an Arduino---he's got some other mini-microcontroller. Here's a screen capture of dialogue referring to missing code:



pololu - Why does my microcontroller's 5V out fail to activate my 5V relay? - Electrical Engineering Stack Exchange

Was rushed for dinner so I'll admit to going through entire posted dialogue too quickly. Tomorrow Morning I'll do tests promised.

Thanks to both of you for the input.

[Rawknees'Turbo]

Originally Posted by Discseven

Was rushed for dinner so I'll admit to going through entire posted dialogue too quickly.

Karl, was this ^^^ and example of ---->

Originally Posted by Discseven

[fitchn]

Karl,

I agree that, if everything is wired/powered correctly, just grounding an input should activate the indicator LED and switch the relay. If that works but the uC doesn't, then you probably have a code and or output driver problem. Your setup should work with either an open-drain or push-pull output topology on your Arduino. However, you mentioned that your control signal was switching correctly so I don't think that is your problem.

Your link only makes me more confident that your current setup can't work. The info you provided was using a 5V relay (SRD-05VDC-SL-C). You don't have a 5V relay, you have a 12V one (SRD-12VDC-SL-C). You mentioned your first effort powered the relay off of 12V and that it still didn't work but I can't help troubleshoot your previous setup without more information. I just don't think your current setup can work, and even if it does it will most likely be unreliable as components will be operating well outside their specified parameters.