RE: Re: [Development] Lights, using two micros.

["Keith Doxey" <ukha@xxxxxxx>]

Using the timing signal to drive the relay requires a R/C circuit to hold
the voltage required to drive the relay. Using an additional pin on the PIC
can drive the relay directly.

Also by using two separate pins allows the same PCB design to be used for
either a dimmer with Relay + Triac or a Switch card with 2 relays for
driving curtains/screens etc.

Zero Crossing would be taken from the low voltage power supply that would
drive all the modules. Therefore is would already be isolated from the
mains, this means only a single opto isolator is requires for a basic
dimmer. A HighEnd option with feedback would require an additional
Quad-Opto.

I looked at the Rabbit to Ethernet diagram last night. The RJ45 socket is a
"special one" with isolation transformers built in. The 8 pins
that connect
to the PCB are NOT the 8 pins in the RJ45 socket. This means there is no
way
to get at the unused pins for our planned "Power over Ethernet"
idea for the
future keypads etc. We would have to terminate the cable onto punchdown
terminals on our PCB and have a short piece of a CAT5 patch cord connected
to that to plug into the RJ45 on the Rabbit. Another option is to user the
RAW Ethernet connections they bring out on the header but that will remove
the Ethernet isolation.

Keith

> -----Original Message-----
> From: Dr John Tankard [mailto:john@xxxxxxx]
> Sent: 03 June 2001 14:34
> To: ukha_d@xxxxxxx
> Subject: [ukha_d] Re: [Development] Lights, using two micros.
>
>
> What did you think about using the triac timing sig to keep the relay
> closed ?
>
> Also do you think we should opto between the Rabbit and the PIC
> rather than between the PIC and Triac, I ask because if the zero volt
> is not opto protected it could feed back to the rabbit in the event
> of a failure. I note that the rabbit to ethernet does have some
> protection.
>
> Keith just found out your Core module was not posted yesterday, So I
> have just gone and done it, will be with you on Tuesday, sorry
>




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