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Successful test :)
Now off to coding part (controlling this via BLE from mobile device).
Thank you @Robin and @allObjects :)
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Thank you @allObjects and @Robin for time you put into this :)
So indeed, all this time I thought that unlocking action is triggered by grounding MK. Analyzes of @allObjects shows that it should be KE. So I double-checked and you're right :) I was grounding KE and put wrong info in one of the first posts in this thread. To my defense this generator is installed in a place that is hard to get to, so I was relying on small mirror to read the labels.
In any case, it's definitely KE that is getting grounded.
I also did a bunch of measurements:
Is the voltmeter an analog needle type or a digital LCD type? Black ground and Red positive probes?
It's a digital LCD type, with black and red probes.
- The voltage drop on on R18 by measuring between MK and MASA. The voltage drop is 9.6V.
- The VAC between X1-1 and X1-2 (the black cables from the coil) and it's 13VAC.
- The drop between MU and MASA is 14V.
- The drop between KE and MASA is only 0.6V (this is what I need to pull-down to ground).
Does this information change anything in values of resistor or transistor type I should use ?
Today I got pulled into work and did not manage to do the shopping. Hopefully tomorrow I will go buy the missing parts :)
Thank you both for all your awesome help:)
- The voltage drop on on R18 by measuring between MK and MASA. The voltage drop is 9.6V.
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Hey Robin,
Thank you for your suggestion on how to test it without endangering MDBT42Q.
I will try to do some shopping for parts tomorrow and give it a try in the evening.Do you have access to a voltmeter?
I do and I was trying to confirm your deduction of what the voltage drop on R18 is. Unfortunately to no avail. I have a trouble identifying this resistor. Unfortunately the labels are just below of them and are not readable. I was trying to recognize it by the color code, but also there doesn't seem to be any that has brown-gray-brown.
If you could pull the circuit out I could inspect the connection on the bottom side, however this is out of question - as I'm not sure I would put it back together :)
Do you have an idea which resistor would it be on the photograph without the wires?
it between X2-6 ground and X2-1 the 11V supply
Just to confirm, the X2-1 will be the black slot with label "1" on top - the one on the bottom of the picture to the right of the slots labeled "EZ". I'm I right?
Thank you Robin :) Have a good night!
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Good morning Robin :)
Ok so it's a little bit hard to make a photo of what I'm shorting in the box, because it's a huge tangle of cables and I can't seem to take a good photo of.
Instead I used the photo with all cables removed and added schematic of how I think I should connect. Please find it attached. I also marked where the electric lock is connected to (EZ label). However I would prefer not to interact with this part. The cables I want to short imitate human pushing the button on the Unifon to open door. The intercom generator controls the time the lock is unlocked. Even if I short it only for a fraction of second the door is unlocked for like ~5 seconds. That's a behavior I like and I want to keep when I trigger opening from Espruino :)
Also I'm attaching the photo of the Unifon internals that helped me figure out what I should be shorting. It's much clearer. On that photo I was shorting inputs labels 10 and 9. This is what allowed me to figure out the colors of cables that I should be shorting downstairs.
What is your mains voltage in your country?
I'm in Poland and the AC standards is 230 V / 50 Hz. Despite my googling effort I can't find what the standard for DC are. I begin to think there is no standard and engineers just make it up as they go:)
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Hi Robin,
One of my favorite learning videos is the exploding LED, around 03:08
You should check out ElectroBoom youtube channel. It's run by Iranian electric technician living in Canada, who is constantly getting shocked or have stuff catch fire. I find it very entertaining :)
Any chance you could provide images of the exposed intercom wiring and how the shorting of pins is done?
I was trying to make the best photo of the wiring I could get, but really it's quite messy, so not easy to make something out.
So I googled around for this intercom model and actually internet came through:) I'm attaching:
- Photo of this board with all cable removed.
- Schematics of correct connections.
- The schematics of the generator.
4.The photo of the actual wiring. It's cluttered and messy.
Unlocking action is triggered by shorting the black and brown cables.
On picture without wires these are labelled MASA (this is polish for ground, black cable) and MK (brown cable).I figured this part out by inspecting how unifon in my home is wired. Also I shorted these two clips with a cable and it opens the lock. I measured there is 0.6V between these wires.
Thank you again for helping me with this :)
- Photo of this board with all cable removed.
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@Robin thank you so much for your response.
I completely agree that using a transitor would be the right way to go. It's also what @allObjects is suggesting (thanks!). If I understand correctly I would connect G to the ground, S to the connector on intercom I want to ground and D to one of GPIO of MDBT42Q. Than I would control it with a code like
analogWrite(TRANSITOR_D, 1)
to close circuit andanalogWrite(TRANSITOR_D, 0)
to brake it again. Is my understanding correct?The only problem I have with this approach that I don't have a transitor at hand :) and if I order one online I will have to put my project to a shelf for a week or two until it's delivered.
I measured the voltage between the circuit I need to short using universal meter. They show 0.6V of difference. And it really looks like unlocking is just triggered by grounding this wire. If I understand correctly this means "pull-down" signal, right?
I reviewed the tutorial with the loop and detecting when it gets grounded. I guess it's slightly different than what I need. The tutorial detects that the voltage has dropped. However in my case I need to cause the voltage to drop and the voltage is supplied by the external source (transformer coil of the intercom). Can you please elaborate on how I could cause a voltage drop on a wire connected to GPIO?
Do you have resistors in the 5K to 10K to 50K range to use as a jumper to test?
I don't. But I do have a universal meter. What should I test for?
Btw, you've probably already noticed I have very little knowledge about microelectronics. I write software for living. This is my toy project to learn something outside my field of expertise.
Thank you again for helping me out.
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Thank you Robin for your response. Let me elaborate.
I have a 3rd party circuit (an intercom). I can take a wire and short two connectors on this circuit and this triggers the unlocking action. I would like to trigger the same behavior using MDBT42Q. I was hoping I would solder two wires to two GPIO pins on the breakout board of MDBT42Q and connect them to these connectors on the intercom circuit. Than I was hoping I would issue a command and MDBT42Q would open circuit between these PINs therefore shorting the connectors and opening the lock.
Am I explaining this right?
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Hi,
I'm working a small project just for fun. I'd like to open an electronic lock through BLE using MDBT42Q.
The unlocking action is triggered by closing circuit between ground and another wire.
I have though I would be able to connect these two wires to some PINs in MDBT42Q brakeout and open circuit between them programatically.However it doesn't seem to work like this.
Can anyway give me a hint of what is the best way to interact with such circuit from MDBT42Q?
Thank you,
Marek Kowalski
That's correct, it's a battery pack, for 3 AAA bateries.
The idea is to eventually power the curcuit from MK connector where I measured I have +9V.
On the video I'm only making a test taking advantage of the fact that in Unifon I have access to same cables so I don't need to take the stairs ;)