Designing a M-Bus master for reading heatmeter

[Jagermeister]

I'll design a brand new MBus master for reading one Mbus slave heatmeter device. I thought that i can design it in a USB Stick way. But im struggling to choose the components. Do you have any suggestions for me? Thank you for your time.

 

[KlausST]

Update: after further readings i come up with this regulator

Where do you see a regulator?

And that's the ready to buy converter as Klaus recommended.

I did not recommend it. And for sure not this wrong wiring.

UART to USB converter with FT232R.

You better review the datsheet and correct your schematic.

Klaus

 

[Jagermeister]

Where do you see a regulator?

By regulator i mean boost converter and Aimtec AM2D-0515DZ is a dual output 5V to +15V/-15V component. Isn't that right?

I did not recommend it. And for sure not this wrong wiring.

What should i change? What's wrong with the wiring, can you explain it to me so that i can fix it? I couldn't find any example wirings in the component's datasheet.

You better review the datsheet and correct your schematic.

I did the wiring based on the datasheet for FT232R, and i didn't get how it's wrong. TXD and RXD are connected, all GND pins are connected. Also i wired VCC and VCCIO together because datasheet says ;

(for the VCCIO pin)
"+1.8V to +5.25V supply to the UART Interface and CBUS group pins(1...3, 5, 6, 9...14, 22, 23). In USB bus powered designs connect this pinto 3V3OUT pin to drive out at +3.3V levels, or connect to VCC to driveout at 5V CMOS level."

And i don't use the remained pins. I added C1,C2 and L1 myself. What exactly wrong in the FT232R wiring so that i can fix it.

Edit: I see that 3V3OUT pin has the connected to the GND using 100nF cap. I'll change it.
Edit2: Also i realised there is an EMI circuit example in the AM2D-Z datasheet. I'm working on it.

 

[KlausST]

By regulator i mean boost converter and Aimtec AM2D-0515DZ is a dual output 5V to +15V/-15V component. Isn't that right?

"Regulating" means there is a setpoint and a feedback (and an error amplifier).
But the AM2D devices are not regulated at all.

But there are truely regulated DCDC converters. But they are more expensive ..a dn advertised to be regulated.
The datasheet uses the term "regulation" (maybe for marketing reasons) but if you look for the regulation specification:
It says the output may change by 1.2% on a 1% input change. This means the output error is worse than the input error --> no regulation.

What should i change? What's wrong with the wiring, can you explain it to me so that i can fix it? I couldn't find any example wirings in the component's datasheet.

It should be obvious that short circuiting the DCDC_negative_output with DCDC_GND_output isn´t a good idea.

I did the wiring based on the datasheet for FT232R, and i didn't get how it's wrong.

missing capacitors, RxD is marked as TxD and vice versa.. capacitor values, inductance instead of a ferrite bead, AGND not connected with DGND .. maybe even more..

Klaus

 

[Jagermeister]

Update:

This screenshot belongs to the AM2D series. Here are some examples of the dual output configuration.

And this is what i came up to. Added a ferrite bead on input and LCs on output. But i don't know how to supply the circuit with this dual output. It will take some time for me to learn this.

missing capacitors, RxD is marked as TxD and vice versa.. capacitor values, inductance instead of a ferrite bead, AGND not connected with DGND .. maybe even more..

3V3OUT pin had a capacitor that i've missed. I fixed that issue. I don't know if there are any capacitors around. Datasheet doesn't say so. And isn't it suppose to wire the RxD to TxD and TxD to RxD? I didn't mark them i connect them with net labels (Main Circuit's RxD port is FT232R's TxD port). I will connect the GND's. Thank you again for your time and interest. You are more than helpful.

Edit: an update from FT232RL;

I added that the datasheet suggests for Shield and VCC. Also added C4 and C5. Fixed TXD/RXD mistake. Connected AGND and GND together. The RESET# and OSCO/OSCI pin are not used neither CBUS pins. I added C7 and C8 for USBD M/P.

@FvM

 

[Jagermeister]

Any suggestions to recent post?
@FvM

KlausST​

 

[KlausST]

Hi,

to be honest, I´m quite confused.
So much schematics, some are similar, some are totally different.
I never know which one is from you and which one is from other sources (internet, datasheet).
Then there are comments in the schematics ... Some are from you, some are not from you, some just don´t fit to the schematic.
I don´t know how to treat them.

My recommendation: post ONE schematic, focus on ONE topic. Ask clear questions (max 3, as text, not in the schematic) referring to the schematic.

(But keep names consistent. If VCC on one schematic is 5V, then don´t use a node with name VCC but for 3.3V.
Try to keep part names unique. If there is a resistor "R1" on one schematic, don´t use a resistor "R1" on a different schematic.
This helps to prevent from misunderstandings, especially on public discussions.
I personally like naming this way: Resistors on schematic page 1 are R100 ... R1xx, on page 2: R200...R2xx)

*****

Example: let´s focus on the power supply.
Let´s say you have two batteries, 12V each, a bunch of cables, and a DVM showing DC values.
Q: how would you wire it all, so that the DVM shows +24V?

If you can solve this. --> just do the same with the output(s) of the DCDC converter. It´s basically the same. (just the values are different)

***

Mind:
* the DVM has two inputs. Usally one is black, the other is red. In most cases the black one is what in your circuit is called "GND" (especially when no other reference is mentioned).
* A DVM measures the voltage of the red node with respect to the black node.
* When you see: "VCC = 3.3V" .. there is no reference mentioned, thus the reference is GND. In detail it means: "The voltage of VCC with respect to GND is 3.3V"
* But when you see: "V_GS = 4V" (like for a MOSFET), then "S" is the reference. In detail it means: "The voltage of G (gate) with respect to S (source) is 4V"

Klaus

 

[Jagermeister]

Update:

Thank you for your informations and guidance.
1- I want to know that is the -15V and +15V placement is true or not. I connected the GND pins on Main to the -15V instead.
2- Is the FT232RL connection true? I followed datasheet and @KlausST 's comments.
3- What would you add to the circuit before starting to layout?

Thank you for your time.

 

[FvM]

You are implementing isolated power supply and signal isolation through opto couplers, why would you short GND(GNDA) to -15V?

J1 is functionless, "GND" at J1 is -15 in the present circuit.

 

[Jagermeister]

Thank you for the reply. I want to make the MBUS1 and MBUS2 output's voltage difference 30V. Yes, J1 is functionless, i want to add an extra connector but not for now.