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ultra-lowest-power data-transfer — Parallax Forums

ultra-lowest-power data-transfer

StefanL38StefanL38 Posts: 2,292
edited 2011-08-22 16:40 in Propeller 1
Hi,

the standard ethernet network cables are based on "twisted pair and differential current". Surely a technology that is very robust against EMV. But it is quite a lot current. My 4-channel switch uses a 3A-powersupply! Just to transfer "some" information.

I'm no real expert about interfaces. I know RS422 is based on differential voltages (not current) but the maximal distance to connect devices is much smaller than using ethernet. If I need only 9600 baud transferrate to exchange data between devices: What kind of interface would you recommend if it should use as less electric power as possible?

This is a non propeller-related question. But there is no sandbox-forum anymore. I estimate that Inside the propeller-forum there are open-minded and experienced EEs (formal graduated or just informal by practicing) If there is a forum this question suits very good into please tell me so and moderator move the thread to this place.

keep the suggestions coming
best regards

Stefan

Comments

  • LeonLeon Posts: 7,620
    edited 2011-08-21 04:57
    Wireless systems can use a lot less power than wired networks.
  • Andrey DemenevAndrey Demenev Posts: 377
    edited 2011-08-21 05:16
    And vice versa
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-21 08:32
    StefanL38 wrote:
    This is a non propeller-related question. But there is no sandbox-forum anymore.
    The General Discussion forum replaced the Sandbox as the place to post threads that don't fit anywhere else.

    The greatest wired distances can be accomplished with a short haul modem, which modulates a carrier with the data, so it can be transmitted longer distances with less power. It's like wireless with a wire. :) Here's one that can work at 9600 baud over a 1.3 mile distance, yet uses less than 6.5mA at 9V:

    -Phil
  • StefanL38StefanL38 Posts: 2,292
    edited 2011-08-21 09:12
    I re-read the description of the general discussion forum. and you are right.
    I remembered it as "questions regarding any Parallax product"

    Thank you very much Phil. 6.5 mA is quite low. If I understand right this modem uses the RS485-specification Is this correct?

    best regards

    Stefan
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-21 09:19
    Stefan,

    The SHM can interface to RS485, but it does not use RS485 to cover those distances. Most likely, it uses analog modulation of some sort over pairs in a 4-conductor telephone cable.

    -Phil
  • Tracy AllenTracy Allen Posts: 6,666
    edited 2011-08-22 09:44
    Stefan,

    What distances are you talking about? RS422 and RS485 are good to over a km at 100 kbs with a decent cable, and the drivers are relatively simple chips that may be put into an extra low-power mode when not in use.

    Do you want your thread moved over to general discussion?
  • Mark_TMark_T Posts: 1,981
    edited 2011-08-22 16:19
    StefanL38 wrote: »
    Hi,

    the standard ethernet network cables are based on "twisted pair and differential current". Surely a technology that is very robust against EMV. But it is quite a lot current. My 4-channel switch uses a 3A-powersupply! Just to transfer "some" information.

    I'm no real expert about interfaces. I know RS422 is based on differential voltages (not current) but the maximal distance to connect devices is much smaller than using ethernet. If I need only 9600 baud transferrate to exchange data between devices: What kind of interface would you recommend if it should use as less electric power as possible?

    Over what distance, using what kind of cable, what level of electronic noise nearby and how reliably? For short-haul I'd suggest CMOS signal and its inverse and a micropower comparator to receive at the other end. 9600 baud is not too tricky (ethernet needs to work at 100Mbit over long distances, a different ball game.)
  • Cluso99Cluso99 Posts: 18,069
    edited 2011-08-22 16:29
    I am happy for the thread to remain here because a lot of comms are done with the prop. Therefore it is relevant for others here.
  • Dr_AculaDr_Acula Posts: 5,484
    edited 2011-08-22 16:40
    RS485 drivers use fairly low currents and I understand go a bit further than RS232. I've had RS232 at 9600 baud through the house going about 30 metres total with unshielded wires and that worked, but it failed at 19200 baud.

    I've also had 1200 baud with straight cmos output with a distance of about 200m.

    I've even played around with ultra low baud rates eg 1 baud, going many kilometres. 1 baud is quite fun because you can attach a led or a buzzer and after a while, get to know some of the bytes. A bit like learning morse code.

    Does it have to be 9600 baud?
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