Marino,
     These are some really good points. I didn't put in a diode because=20
of the forward voltage drop. I'm using a 5 volt regulated supply and 4.5=20
volts would be right at the limit of what a 628A will tolerate. I'm=20
going to put these suggestions away for another day. I appreciate this.
Thanks,
rich!

On 9/17/2015 6:34 AM, Isaac Marino Bavaresco wrote:
> Richard,
>
>
> It is a good idea to always provide some sort of reversal polarity
> protection to circuits. It is very common for equipment to be connected
> with the wrong polarity or a wrong power adapter.
>
> There are several approaches, suitable for various circuit requirements.
>
> 1) Just use a diode in series with the power input. Suitable when your
> circuit consumes a moderate current and you have a voltage regulator in
> the input or can tolerate a small voltage drop.
>
> 2) Use a fuse in series with the power input and a powerful diode
> connected cathode after the fuse and anode to ground. Your diode must be
> strong enough to ensure the fuse will blow before the diode is damaged.
> The advantage is that you don't have the Vf loss from the diode when the
> circuit is operating.
>
> 3) Use a power P-Channel MOSFET with its Drain pin connected to the
> power supply, Gate to ground and Source as output to the circuit. This
> circuit can be used for voltages up to approx. 20V, which usually is the
> Gate-Source breakdown voltage. With the addition of a Zener diode and a
> resistor this limit can be raised.
> This circuit can be used for really high currents with very little
> energy loss. If you add another MOSFET in series in the opposite
> direction plus a TL431, another smaller MOSFET and some resistors, you
> have overvoltage protection also.
>
> 4) Use a relay with its coil with a diode in series connected to the
> power input. Use the normally-open contact to power your circuit. This
> method can be used for any current and voltage ranges and the only loss
> is the relay's coil current.
>
> Cheers,
>
> Isaac
>
>
> Em 17/09/2015 03:43, Richard R. Pope escreveu:
>> Bob and et al,
>>       Well I just make a goof! I was very fortunate. I hooked the power
>> to my control board up the wrong way. The PICs are tough little
>> monsters. Even though the power was hooked up the wrong way for almost
>> twenty minutes all of the PICs are fine. It looks like all that I
>> damaged were the tantalum capacitors. Wow! Good news. I'll be more
>> careful from now on. I appreciate all of the help that everyone has
>> given me.
>> Thanks,
>>
>
>

--=20
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