FreeBSD and controlling an alarm via relay
smithi at nimnet.asn.au
Wed Jul 6 12:40:11 UTC 2011
Dropping multimedia@ cc as this seems pretty well 100% hardware .. but
I'm not subscribed to hardware@ so please cc me from there.
On Wed, 6 Jul 2011, Achilleas Mantzios wrote:
> another thing that puzzles me is power.
> This board : http://www.ebay.co.uk/itm/USB-Eight-Channel-Relay-Board-RS232-Serial-Controlled-/110710333092?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item19c6d99ea4
> needs VDC 12V supply
> while this one : http://www.ebay.co.uk/itm/USB-Four-4-Relay-Module-Board-Home-Automation-/180646300804?pt=LH_DefaultDomain_0&hash=item2a0f5bcc84
> is self powered from USB.
> batteries do not come cheap, and having an extra AC/DC adaptor is not very good either ...
That 4-relay one might better suit your application then, if FreeBSD usb
recognises it. It seems to use the same (FTDI?) drivers under windows
as the other one, but I know almost nought about USB device detection.
> another thing is the relay parameters, i see various figures :
> Relay parameters: 5V / 72mA, 15A/24VDC (120VAC), 10A/250VAC or
> Each switch 12VDC/15A or 240VAC/10A or
> Open (No) and Closed (NC) Contacts rated for voltages: 12VDC/15A; 24VDC/15A; 125VAC/15A; 250VAC/10A
> my specific application i want to drive is this wireless xmitter :
> Should i assume my device that i want my relay to control will have voltage of 3V?
> for which Voltage/Ampere figures should i opt? are those figures crucial?
5V / 72mA is the relay solenoid drive current. 4 of these switched on
would use ~300mA, leaving 100mA for the other board circuitry. The 12V
board's relays use the same drive power, 360mW, ie 12V @ 30mA.
The relay switched contacts are rated at 12VDC to 15A (180W) or 240VAC
to 10A (2.4kW!), whereas your MCT 100 is only watching for NC contacts
to open; closed circuit current will be a few mA at most and you won't
see more than 5V over the open contacts .. ie, not an issue.
> thanx a lot
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