Short circuit generator

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ahull
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Re: Short circuit generator

Post by ahull » Thu Aug 10, 2017 7:55 pm

- Andy Hull -

konczakp
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Re: Short circuit generator

Post by konczakp » Fri Aug 11, 2017 8:00 am

Yes I've seen this doc but it is about how to setup and connect the base rather then how the base is sending data and interfacing with the receivers.
I also don't have any device fast enough to measure voltage in time of 16us when it is going to low. I've attached to my earlier post file with captured pulses from logic analyzer but this capture was made with voltage divider so I don't know if it is going really low to 0v. But I could imagine that the uc is connected via capacitor to the 12V and when the line goes low then the uc is powered for a very short time from capacitor. But maybe this is a bad approach. I don't have knowledge about it. I also know that when the base is sending receiver number (address) at the beginning then this communication is digital and after that everything goes in analog way. It is like:
power line is at 12-14V
1. long low for reset
2. receiver number
3. wait time
4. start to ring (few rings with delays between each ring) and wait for off-hook to start the conversation.
5. off-hook - power line is going to about 5V and analog communication is started
6. on-hook when end of talk - power line goes to 12V
I haven't measure the current drawn by the receiver because the current is meaningful only when You want to pick-up the phone and start the conversation. I know that there are no SSR switches going so fast (I wrote it in my first post). How can I distinguish how it really works and what to do to to be a second base in the same circuit?

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ahull
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Re: Short circuit generator

Post by ahull » Fri Aug 11, 2017 9:06 am

I think a bit of reverse engineering may be in order.
Maybe its time to take the cover off one of the slaves, and take some pictures, so we can identify the chipset and circuitry involved in communications.
Can you borrow an oscilloscope? By my back of the envelope calculation, a 16uS period suggests a relatively low bandwidth signal of the order of 62,500 Hz (62.5kHz), so you should be able to see that on the "pig-o-scope" or any of the low cost scopes from ebay/ali express.
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konczakp
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Re: Short circuit generator

Post by konczakp » Fri Aug 11, 2017 10:16 am

Ok so I've made a few calls and I will borrow today 200HHz scope. Write me then please what to measure an when ?

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ahull
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Re: Short circuit generator

Post by ahull » Fri Aug 11, 2017 1:51 pm

konczakp wrote:
Fri Aug 11, 2017 10:16 am
Ok so I've made a few calls and I will borrow today 200HHz scope. Write me then please what to measure an when ?
You will need to take a few pictures of the waveforms, so we can see what is what.
- Andy Hull -

dwight
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Re: Short circuit generator

Post by dwight » Sat Aug 12, 2017 4:26 am

Maybe you might look at it a different way. I would suspect that the
units on the line all have local regulators.
Why not just put a low level signal on the line and either tap it off with
a capacitor or even transformer.
You could use a simple tone or even a phase modulation that rides on
top of the DC level.
Most regulators can handle 100Hz with good isolation.
Most power supplies that put out amps, do not take kindly to shorts.
Dwight

konczakp
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Re: Short circuit generator

Post by konczakp » Sat Aug 12, 2017 4:59 pm

Ok, so I've made some measurements and pictures. This is how the receiver look like from inside.

Side one:
IMG_20170812_182241.jpg
IMG_20170812_182241.jpg (79.09 KiB) Viewed 63 times

Side two:
IMG_20170812_182351.jpg
IMG_20170812_182351.jpg (89.78 KiB) Viewed 63 times

On the board there are HCF4093 and 74HC40103D.

I have recorded all he transmission between Base and Receiver but I encountered a small problem. I couldn't catch the first stage when the receiver number is being dialed. And I don't know why (I will get back to this at the end of this message). But rest of the communication is fine.
Here is how it looks like (I hope I did correctly). I used cursors to measure length and voltage.

I couldn't add more than 3 files so I will post more than one message
IMG_20170812_171253.jpg
IMG_20170812_171253.jpg (85.99 KiB) Viewed 63 times

konczakp
Posts: 187
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Re: Short circuit generator

Post by konczakp » Sat Aug 12, 2017 5:01 pm

IMG_20170812_172537.jpg
IMG_20170812_172537.jpg (90.21 KiB) Viewed 63 times
IMG_20170812_171533.jpg
IMG_20170812_171533.jpg (84.73 KiB) Viewed 63 times
IMG_20170812_171427.jpg
IMG_20170812_171427.jpg (80.64 KiB) Viewed 63 times

konczakp
Posts: 187
Joined: Thu Jul 14, 2016 4:17 pm

Re: Short circuit generator

Post by konczakp » Sat Aug 12, 2017 5:05 pm

IMG_20170812_172750.jpg
IMG_20170812_172750.jpg (95.09 KiB) Viewed 63 times
IMG_20170812_172626.jpg
IMG_20170812_172626.jpg (78.89 KiB) Viewed 63 times

.
Now back to the problem of dialing number of the receiver. I only got something like this below but I don't think that this is correct.
.
IMG_20170812_173441.jpg
IMG_20170812_173441.jpg (95.83 KiB) Viewed 63 times

konczakp
Posts: 187
Joined: Thu Jul 14, 2016 4:17 pm

Re: Short circuit generator

Post by konczakp » Sat Aug 12, 2017 5:11 pm

IMG_20170812_173405.jpg
IMG_20170812_173405.jpg (88.53 KiB) Viewed 63 times

.
So I've made some experiment with my maple on which I've generated very fast impulses (same as the base is giving) and those have recorded fine. Like below
.
IMG_20170812_181648.jpg
IMG_20170812_181648.jpg (80.23 KiB) Viewed 63 times
IMG_20170812_181803.jpg
IMG_20170812_181803.jpg (83.19 KiB) Viewed 63 times
.

But this is impossible that I'm unable to record those spikes from receiver because as You have seen Logic Analyzer was able to detect them. But despite of that receiver number it seems that the voltage is getting 0v for Low. What do You think?
.

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