Perhaps it's just me,but this doesn't seem like it would need an
optocoupler. If you want to use a relay, just put a 1N914 or 1N4148 diode
across the coil to prevent voltage spikes and it should be fine. Just be
sure that your relay coil doesn't need more current than the pic pin can
source.

I'd be tempted to solve the whole problem with a power darlington (like one
of the TIP series). Just put the strike between 5V and the darlington's
collector. Base to the PIC via a 4.7k resistor, emitter to ground. Add an
additional 1.5k resistor from base to ground,to prevent self turn-on.

In either case, put a 1N4004 or similar diode across the strike (with
cathode toward positive - reverse biased) to prevent voltage spikes. A
capacitor such as a 0.1 uF ceramic disc would also be good across the
strike. I take it that the strike contains a motor?

BTW, do you need to reverse the strike (to unlock)? If so, an H-bridge
would be your best bet.

Sean

At 12:57 PM 10/17/99 -0400, you wrote:
>99 11:03:17 am@
>
>>
>> Hey everyone,
>>
>> I'm using a 16F84 in a keyless entry project.  In this project a need to
>> unlock an electric door strike from port a.  All of the door strikes
>> that I have found run off of either 24V@120mA,  12V@280mA, or 5V at 1A
>> (or close to those currents).  The 16F84 will only source 50mA.  Does
>> anyone have any suggestion to make this work.  Should I amplify the
>> current and use an optocoupler or something else.
>
>My standard way of dring stuff like this is using relays that are
>connected to the PIC via an optocoupler.
>
>BAJ
>
|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
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