AVR Freaks

Each Head has seperate DC-DC converter. these converters are fed through a roller bearing contact. There are 2 roller bearing contacts
One contact:36Vac
Other Contact: GND

The DC-Dc converter converts this 36Vac to a 0..50A upto 8V adjustable current source. The value of the set current should be send to the moving unit.

Wireless is not effective because each segment has different current set values. I send a photo of the system . total length of the elliptic path is 25m.
Segment 1 : 1m Electrical Current value1
Segment 2 : 2m Electrical Current value1
Segment 3 : 6m Electrical Current value1
Segment 4 : 3m Electrical Current value1
Segment 5 : 6m Electrical Current value1

I thought abaout changing the frequency of the power bus of each segment and count the frequency on the slave.
For exampel I send 36Vac at 3000Hz this means 30A current set value.

Each moving unit is 10cm wide and can source 50A upto 8V. it means if a segment is 6m long I should modulate a frequency on 36Vac at 500A.

But it is a very corrosive enviroment. (chromic acid ).
So the bearing contact is not reliable for data transmission.

for power transmisson on a noisy prelling contact I rely on a high voltage buck converter. Input:36Vac output is 0..50A upto 8V , so if a prell or noise induced on the bearing, the buck converter will compensate it throgh internal stored energy margin and regulation down to 8V.

But for data transmission, I can not feel comfort.

An aggragte should not miss a packet. Because if missed. The product it is processing will be destroyed.

If wireless is implemented the range sgould be very tight up to 5cm.So that each segment can have its own wireless sender.

The parts move with up to 20cm/sec.

Best regards.

I also thought of using irfrared. But the enviroment has a severe acid cloud. It will be sucked by the ventilation, but anyhow it seems to me risky to rely on a shiny clean led surface.

I also agree that some range/band for signal data should be defined and only these in-range data should be processed.

I have the idea to use 2 signals they are 2 pwm signals that are phase shifted to each other.

Lets assume each PWM has a frequency of 500Hz.

I define some bands of phase shifts

Band1= 100us-200us
Band2= 400us-500us
Band3= 700us-800us

the slave controller measures the phase difference.
it throws out the ones that are not in band range.

The filtered data is sorted. And the most equal series from 100 in range measurements data set should be considered the right data. I believe I should use standard deviation formula to decide which set and number of series should be the same and can be considered as right data.

Example I have from 100 in band measurements:

42 times 410us-412us
12 times 400us-402us
5 times ....
2 times ....
......

It is the question how to find the minimum number so that it can be considered as right data. In this case I have 42 times 410us to 412 us range . So what is the minimal number of the most frequnt range so that it can be considered as right.
(ex: except 42 what if the maximum frequent equal data is 32, is it enough according to the theory of standard deviation?

Below : standard deviation has +/- %31.2. So if 32 values out of 100 are the same , I accept them as right data?!?!?

Or is this %32.1 also data set dependant?. And should be calculated dynamically?

Any ideas?

http://en.wikipedia.org/wiki/Sta...

Yes,
Inductive data transmission seems the best, robust to acid cloud .(sender and receiver can be fully encapsulated by a thin plastic film).

I am also investigating a transformer like stucture where the one half of the E core is 1cm apart from the other half. Just think abaout 2 seperate coils and they have 1cm air distance. If I modulate a suitable signal on the first coil , I can get information on the second coil.

But in my case I should consider the mechanical tolerances. 1cm (10mm) air gap will swing with a tolerance of +/-2mm it can be 8mm or 12mm according to the tolerances of the mechanical construction.

Have anyone tried something like that , maybe a PCB coil with a PWM and 10mm apart another PCB coil, o good proper modulation scheme (ex, phase shift modulation or frequency shift keying, etc.). It will be more immune than a physical contact in acid cloud .

I should begin searching spi to rfid ics.

MCU spi to rfid ------ rfid to spi MCU

I always thought that rfid is not a bus system but a active - passive transmission (libraries, bookstores etc.)

But if both sides can be active (as MCUs) I should try to implement it.

Also importants details : Can Rfid do a multicast or broadcast to all slaves? Ex: I tried to figure out ASI bus. But after I discovered that it can not do multicast, i thought it would be a headache to send to all adresses in a loop.

Any ideas for spi to rfi ics and multicast.

I believe I can limit the range to 15 to 20cm so that each segment can have its own range.

Rfid or Optical? .this is the question.

I can built a dark encloser from extruded plastic for the sender and receiver. So that no sunlight pass through. The problem there is if any contanimation or dust of acid is collected in this enclosure. I must examine .

Any recommendations for rfid to spi chips and 38Khz irda transmitters so that I can try both on a prototype where acid cloud will be more severe than normal condition. IMHO best way is to test it under these conditions.

Any name/vendor for RFID to spi and IR transmitter to spi.

best regards.

I examined the MFRC522

The active unit sends data to a passive card, which can be read . I can not figure out how I can connect the passive card (IEC 14443) to spi to read the data that is written by MFRC522.

Is it possible to connect the passive card to spi in a glue logic. Or are there some cards that sotre the data in eeprom that can also be read by spi externally.

The long way is to write the data to passive cad and the slaves read from these passive cards through a seperate MFRC522.

the card is 10mm apart from the elliptical path. it will be updated by host rc522 and read by slave rc522 that is attached on moving slaves. But i dont know if host can write and other slaves can read from the same card. There must be also collision avoidance etc.

Best and shortest way seems to read the cadrd data through spi and install cards and readers on the moving unit.

Any recommendations to read data from passive card thgough other slave rather than the host that has written into it.

How abaout multicast. Can all cards have the same adress. If so, how will they reply back to verify data?

Sorry, my last post is lost. I send it gain

aggregate : set of machines (I mean carriage)

prell (word from other language): contact debounce or untight contact, discountinuty in contact resistence reliability.

Any clue , starting point how I can simulate rfid card through spi?. Any starting point?

This is a very interesting hack. Not only power, but even the oscillator frequency is derived from the antenna.

But in my case my rfid card emulation mcu is powered and clocked by external source , so it will be harder to convert the code to my needs. Especially the synchronization of my mcu crystal freq against abtenna frequency.

Are there any full active rfid cad emulation mcu example.

My sender rc522 will have a PCB trace. My coil card has also a pcb trace but the decoding of the RFid on the card side is not clear to me, if there would be any active IC on the card side just like rc522 on the market, it would be a great help. Maybe I can try to misuse the rc522 so that it functions as a rfid card emulator.

the master rc522 sends rfid data and the card emulation rc522 replies back.
Is my logic straightforward or forked to uncertainity?