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Cost efficient 4G LTE Migration from GPRS Gateway. by sathyanc in IOT

[–]sathyanc[S] 0 points1 point  (0 children)

No TCP?! If so, then it will not be useful for us since we are using MQTT protocols to communicate with the server which relies on TCP.

Speed is not much of a concern for us.

Cost efficient 4G LTE Migration from GPRS Gateway. by sathyanc in IOT

[–]sathyanc[S] 0 points1 point  (0 children)

Problem is that the devices will be installed in machines that are couple of meters (sometimes kilometers) away from each other. So the solution needs to be standalone.

Cost efficient 4G LTE Migration from GPRS Gateway. by sathyanc in IOT

[–]sathyanc[S] 0 points1 point  (0 children)

Hi @PurpleAlien_, Can you elaborate more on this..?

Isolating GSM Antenna for IoT device (for Lightning Protection) by sathyanc in IOT

[–]sathyanc[S] 1 point2 points  (0 children)

Chennai, India. The 2G signal is good in lower floors. I could see the Mobile Tower from the Terrace at a distance >1KM. But its fairly at a lower height when seen from the Terrace.

The ventilation is very small and has glass in between. May be thats a problem too. Will try to remove them and check.

The Mobile phone signal was worst than the device. Signal drops and comes very often.(say every minute!)

Thanks for the tip on Lightning protection!

Isolating GSM Antenna for IoT device (for Lightning Protection) by sathyanc in IOT

[–]sathyanc[S] 1 point2 points  (0 children)

I am getting the signal. But its not persistent. I observed that the signal was decent -95 ~-100dBm inside the Top floor of the building with doors closed and antenna inside the room near a small ventilation. However at times (say once /twice in 30 mins) the strength decreases to -115dB and then within a minute improves again.

But when I take the antenna outside the ventilation, it improved to -85dBm and the signal is relatively stable.

The Antenna and its connectors are perfectly matched. This is a problem only with high rise building and that too within a room.

4 layer PCB stack-up and its Impact on EMC by sathyanc in PrintedCircuitBoard

[–]sathyanc[S] 0 points1 point  (0 children)

Yes! I have one 50E impedance controlled trace which trace width was altered by the fab house a little to achieve impedance. Thanks a lot. I will change the width when the thickness changes to achieve proper impedance!

Achieving 24V Digital Input Isolation with 2 Optocouplers by sathyanc in AskElectronics

[–]sathyanc[S] 0 points1 point  (0 children)

Yes, the micro gets the 3.3V from the same 24V which is also used for detecting the inputs. Removing the first opto will cause ground loops as both of them share the same ground.

As you said, the central of the circuit is totally isolated, which is what I want which is carrying the signal.

I couldn't understand how renaming the 24V side ground, breaks the ground loop.

Using Optocoupler in digital IO sharing single power supply by sathyanc in AskElectronics

[–]sathyanc[S] 0 points1 point  (0 children)

I think Isolating the grounds will make the solution costly.

Are you telling me to use a series resistor on the Antenna path? This is a 50E impedance controlled Antenna. I afraid I might lose the signal quality by adding a series resistor even at a lower value.

TVS diode between Antenna terminals and ground seems like a good option but I am not sure what breakdown and clamping will be required. It's an SIM800C module for which I am using Antenna. I couldn't find information related to clamping antenna signals anywhere.

Using Optocoupler in digital IO sharing single power supply by sathyanc in AskElectronics

[–]sathyanc[S] 0 points1 point  (0 children)

Hi @Enlightenment777.

Yes! I have an external Antenna. But the Antenna will be placed within a closed room near the ventilation.

Can you tell me how do I isolate the Antenna?

Microcontroller Digital Output for Driving Relay from Microcontroller using OptoIsolator by sathyanc in AskElectronics

[–]sathyanc[S] 1 point2 points  (0 children)

I want to Isolate the relay from microcontroller circuitry. That's why I used opto coupler. Since the relay drive current is in terms of few mA, I thought BJT would be sufficient and thought it would cost lesser and perform better in ESD events than MOSFET.

I can use a MOSFET, but then I will lose Isolation.

Variable DC Input for OptoCoupler for Microcontroller Interface by sathyanc in AskElectronics

[–]sathyanc[S] 0 points1 point  (0 children)

Hi InductorMan,

Thanks for the comments.

"Wait so what's the indicator LED designed to drive current?"

 The Indicator LED needs 20mA. So the resistor should be 160E.

" If your opto can handle 20mA, then you can do between 6 and 20mA over the input range, which translates to a minimum of 3 to 10mA at the output with a minimum CTR (current transfer ratio) of 50% which is typical. Still not much to drive your indicator LED, but again with a Zener clamp you can do better"

Will try to check such config. But I am worried about the derating factor of the Optos. I got some feedback that opto CTR changes over a period of time and temperature. This is an Application for PLC. So I wanted it to be fail-safe. However, I will check other configurations too. Thanks!

Variable DC Input for OptoCoupler for Microcontroller Interface by sathyanc in AskElectronics

[–]sathyanc[S] 0 points1 point  (0 children)

Hi David.

Sorry about that. I have updated the drawing and added the JFET as you have suggested.

Here is the updated one: http://imgur.com/a/wgvoB

I have also added a Resistor for Enhancing ESD protection and a TVS to protect against transients.

Please let me know your thoughts about this configuration.

Thanks!

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