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Low Current Relays / Schematics — Parallax Forums

Low Current Relays / Schematics

ValchrisValchris Posts: 3
edited 2008-01-18 18:51 in Learn with BlocklyProp
Hello,
I'm in my last year of high school engineering and have been working on a fairly extensive robotic project. Right now I've been stonewalled by a problem with parallax not having enough power to switch relays. We previously had 12v relays (and i need 10 of them). I acquired 5v relays the other day but have been unable to come up with a schematic on how to wire them. There made by Omron, and even searching the Omron site they seem to not exist! The closest thing we could find to our relays is in this pdf i attached. On page 5 An image is shown of a g5AK-237P. (Our Relays are g5AK-237P-27) I cannot understand the schematic. If anyone could be of assistance in giving me a better idea of what pins are what i would greatly appreciate it!. Thanks in advance
pdf
pdf
G5A.pdf
136K
G5A.pdf 135.6K

Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2008-01-17 16:07
    A typical Relay Driver chip would be a Darlington chip, ULN2008 or so. This has its own connection to Vdd, and can drive MUCH more current than the BS2 I/O pins.
  • KMoffettKMoffett Posts: 7
    edited 2008-01-17 16:19
    What you have are two-coil latching relays. These require a brief ( >5.0mSec) 5 volt pulse on the SET coil to turn the relay ON. After the Set pulse, the relay stays (latched) ON. A pulse on the RESET coil turns the relay OFF, and it stays OFF. The attached schematic shows wiring with driver transistors and protection diodes. Though I have not tried this, I think it will work. If you are used to using normal, single coil, non-latching relays, these may complicate things for you.

    Ken
    Latching Relay.jpg
    425 x 257 - 16K
  • ValchrisValchris Posts: 3
    edited 2008-01-18 18:09
    Thanks for the schematic and your help! I've got my relays working properly now, (although after setting up my 3rd of 10 relay i was required to add another power supply in parallel.) Your diodes serve only a protection for components correct? I've currently wired it without diodes and all seems well, just want to confirm they don't have another role.
    Thanks
  • FranklinFranklin Posts: 4,747
    edited 2008-01-18 18:12
    The diodes are for protection and if you don't care if your stamp is destroyed you can leave them out.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    - Stephen
  • KMoffettKMoffett Posts: 7
    edited 2008-01-18 18:22
    Also, since the relays are latching, they will remain in the last state they were in when you powered-down your system. They will be in that state when you power-up your system, so that could be a problem compared with normal relays.

    Ken
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-01-18 18:51
    "only protection for components"? You say that like it's not important. When you de-energize the relay coil, a current 'pulse' is generated which tends to destroy the drivers behind the BS2 I/O pin. This damage adds up, and eventually (10 activations? 100 activations?) will destroy the I/O drivers.

    So YES you need the "protection diodes", they ARE important for reliability, if nothing else.

    Do your relays need to be switched at the same time?· If you can switch them one at a time, that might reduce your current requirements.
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