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Jun 20, 2017, 04:03 AM
Durability Tester
Quote:
Originally Posted by JulianGoesPro
I was looking through Banggood and at the Wolf stuff and then remebered I had saved a link to a 433 module some time ago... I know so little about the 433 hardware but this kind of looks different (I guess because of the shield?)




Price seems low for 1W, doesn't it?
Can it run ULRS?
there is already a LRS project using those modules
https://www.rcgroups.com/forums/show...with-telemetry
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Jun 20, 2017, 06:07 AM
Registered User
Quote:
Originally Posted by flipflap
Not sure yet for the best value, but it's between pins GPIO1 & TX_ON. See attached image to locate the pins.
Looks like this design change is coming right when I am finalizing the design of the "Penguin" Board.

Captain! should I hold the design ? or make a pad for 0603 resistor any way instead connecting those two pin with PCB traces ? ( As a side question, what is the thinnest trace width safe for such signal Net ? 10mil ? or can I go to 6-7mil, minimum trace width supported by OSH Park) ?
Jun 20, 2017, 06:46 AM
Registered User
Quote:
Originally Posted by ifuh
on banggod two of the pictures show an equipment with label N1201 , not N1201SA
I can see you received the one with 'N1201SA'
Do you know maybe if there is any difference?

Its this one 137mhz-2700mhz https://www.banggood.com/N1201SA-UV-...rmmds=category
Jun 20, 2017, 07:14 AM
Registered User
Thread OP
Quote:
Originally Posted by ujjwaana
Looks like this design change is coming right when I am finalizing the design of the "Penguin" Board.

Captain! should I hold the design ? or make a pad for 0603 resistor any way instead connecting those two pin with PCB traces ? ( As a side question, what is the thinnest trace width safe for such signal Net ? 10mil ? or can I go to 6-7mil, minimum trace width supported by OSH Park) ?
I didn't saw the schematic yet, that would be interesting to check in more detail. Yes I'd allow pads for a resistor, maybe shunted by a trace that could be easily cut.

All the tracks except power tracks will carry very little current, I'd say that 6-7 mils should be sufficient, but would this size have significant advantages ? I think 10 mil is better because occasionally users will want to desolder the RFM or other components and thin tracks could be more fragile for these operations. (But I'm maybe old school on these topics)
Jun 20, 2017, 10:54 AM
Registered User
Dancy's Avatar
Quote:
Originally Posted by Dancy
I thought we had this list published already but I can't find it so here it is again.

https://1drv.ms/x/s!AobIOw0dQmYNgoNlqP4xybPmPVyOIw
I notice someone was looking for the part list for the Sami boards. Here it is again. Ben, perhaps you can copy it to the Lux site to make it more accessible?

the file has links to most parts with both Mouser and DigiKey

PS, Sorry Ben, I see you have a link already!
Last edited by Dancy; Jun 20, 2017 at 10:58 AM. Reason: opps!
Jun 20, 2017, 12:55 PM
Rana
Update in traced hand sketch schematic as on 20th June 2017:

There is update in the traced hand sketch schematic of the RFM23BP module. Collector of the PNP bias transistor (which switches on - off the RF power MOSFET), also goes to the base of RF driver NPN transistor with SMD marking "R25", via 1.5K ohm resistor and then an inductor (created on the PCB via copper track).

There is also a 100nF capacitor connected between the collector of the miniature PNP bias transistor and GND.

Now, with this information, I reaches the conclusion that this miniature PNP has and additional load of +ve biasing the RF driver transistor R25. Already there is no base resistor between the base of this miniature PNP biase transistor and the GP I/O 1 which makes it much prone to failure due to excessive base emitter current (also analysed by Ben).

This recent information puts stamp on the the fact that there is a design flaw in RFM23BP which increases the failure rate and that is a missing resistor between base of the miniature PNP bias transistor and GP I/O1.

Any regular TO-92 package BC556, BC557 transistors can be used to achieve the functionality of this miniature PNP bias transistor but this would require some small wiring.

With this new information, it has also become clear that RF driver transistor(s) are not operating in Class-C but just in Class-A only.

Due to time issue I am unable to devote much and came house today evening only and have to rush out tomorrow again. Once I again reaches back, I would possibly suggest optimum modification.

Update 21st June 2017:
I have added two images here and to my main old post. These give more details about the schematic on the PCB.
The other image shows how to use BC556 or BC557 TO-92 package transistor as an alternative to miniature PNP transistor which goes faulty due to design issue on not using resistor between GP I/O1 and base of this PNP transistor.

I have given general idea, its upto the user, where to place the through hole to-92 package transistor BC557 on the board but one thing must be kept in mind is to keep it away from RF power mosfet and its output inductors in order to prevent parasitic value change of RF components and to avoid RF injection on the base of the transistor.
Last edited by narpat007; Jun 21, 2017 at 11:32 PM.
Jun 20, 2017, 02:22 PM
Registered User
RocketMouse's Avatar
Made some extra cooling for the transistor.
Jun 20, 2017, 04:42 PM
Registered User
Nothing to see here
Last edited by yak-54; Feb 22, 2018 at 03:43 AM.
Jun 20, 2017, 05:00 PM
Registered User
Quote:
Originally Posted by yak-54
where did you get that cover from ?
Thats the standard Shielding for RFM23BP modules . Considering the surface area, they can prove good head sink for that Tiny Transistor and even the main RF MOSFET .

https://www.aliexpress.com/item/RFM2...608.0.0.qd0p8X
Jun 20, 2017, 05:02 PM
Registered User
Thread OP
Quote:
Originally Posted by narpat007
Update in traced hand sketch schematic as on 20th June 2017:

There is update in the traced hand sketch schematic of the RFM23BP module. Collector of the PNP bias transistor (which switches on - off the RF power MOSFET), also goes to the base of RF driver NPN transistor with SMD marking "R25", via 1.5K ohm resistor and then an inductor (created on the PCB via copper track).

There is also a 100nF capacitor connected between the collector of the miniature PNP bias transistor and GND.

Now, with this information, I reaches the conclusion that this miniature PNP has and additional load of +ve biasing the RF driver transistor R25. Already there is no base resistor between the base of this miniature PNP biase transistor and the GP I/O 1 which makes it much prone to failure due to excessive base emitter current (also analysed by Ben).

This recent information puts stamp on the the fact that there is a design flaw in RFM23BP which increases the failure rate and that is a missing resistor between base of the miniature PNP bias transistor and GP I/O1.

Any regular TO-92 package BC556, BC557 transistors can be used to achieve the functionality of this miniature PNP bias transistor but this would require some small wiring.

With this new information, it has also become clear that RF driver transistor(s) are not operating in Class-C but just in Class-A only.

Due to time issue I am unable to devote much and came house today evening only and have to rush out tomorrow again. Once I again reaches back, I would possibly suggest optimum modification.
Thanks ! I've updated the site with your updated schematic : http://www.itluxembourg.lu/site/2-5w-narpat-mod/

Now could it be that it's acting as a class E rf amplifier ?

It looks very similar to this schematic of a class E amplifier :



In this type of amplifier, the mosfet is driven as a switch and not in linear mode like for a class A.

That would explain also why the RFM23BP isn't very linear with the output power parameter, the power transistor doesn't work in linear zone but in switching mode. The advantage of this configuration is also that the RF transistor doesn't have to dissipate much power, it's the most efficient amplifier class. It's also advantageous for the small chip as it only has to generate a square signal rather than sinusoidal, and it explains why the same chip can generate signals in the 433, 868MHz and 915 MHz bands. Only the passive components of the RFM module have to get a different value for every frequency band.
Jun 20, 2017, 05:15 PM
Registered User
Nothing to see here
Last edited by yak-54; Feb 22, 2018 at 03:35 AM.
Jun 21, 2017, 01:08 AM
Registered User
RocketMouse's Avatar
In fact there is another small element at the picture besides the transistor that also gets quite hot.
Is this normal?



Jun 21, 2017, 02:22 AM
Registered User
Nothing to see here
Last edited by yak-54; Feb 22, 2018 at 03:35 AM.
Jun 21, 2017, 03:36 AM
Registered User
RocketMouse's Avatar
I don't know what do you mean by 5V battery. Most of us use Lipo and this is 8V or 4V.
I'll try to use 5V Ldo, but I'm not sure that there can be a connection between the power source and this part overheating.

Actually all Wolf LRSs embeded with these crappy becs. And there are many other projects that use 1584 becs and they didn't complain much.
Here is not such a crappy test result of this BEC.

On the bench: D-SUN and Pololu regulators (UBECs) (12 min 43 sec)
Jun 21, 2017, 05:52 AM
Rana
Hi Ben !

Pls find my comments embedded within your message below;

Quote:
Originally Posted by flipflap
Thanks ! I've updated the site with your updated schematic : http://www.itluxembourg.lu/site/2-5w-narpat-mod/
Narpat: You are more than welcome Ben.

Now could it be that it's acting as a class E rf amplifier ?

It looks very similar to this schematic of a class E amplifier :


Narpat: The RF power MOSFET receives +ve biase via 439 ohms resistor connected to the collector of miniature PNP transistor. So it can be in class-C or class-E. Same is the case with RF driver NPN transistor(s) "R25".

In this type of amplifier, the mosfet is driven as a switch and not in linear mode like for a class A.
Narpat: The RF power amplifier schematic you have shown based on N-Channel MOSFET, is class-C amplifier where the MOSFET switches on during the peak top portion of the carrier RF signal.

That would explain also why the RFM23BP isn't very linear with the output power parameter, the power transistor doesn't work in linear zone but in switching mode. The advantage of this configuration is also that the RF transistor doesn't have to dissipate much power, it's the most efficient amplifier class. It's also advantageous for the small chip as it only has to generate a square signal rather than sinusoidal, and it explains why the same chip can generate signals in the 433, 868MHz and 915 MHz bands. Only the passive components of the RFM module have to get a different value for every frequency band.
Narpat: One thing quite good about the RFM23BP is that in the schematic design it is kept in mind to save power and avoid running RF driver NPN transistor "R25" by providing +ve bias to the driver transistor via miniature PNP transistor, which is being controlled by GP I/O 1.
So, when RF23B chip shuts off RF transmission, both rf driver and rf power amplifier are shut down and not taking any current.
But really the most bad thing those guys did is that they used so small package for the PNP transistor and the critical thing they forgot to keep a base resistor of this pnp transistor to GP I/O 1.
Pls have a look at the new image added which gives the information about the schematic on the PCB.


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