[chbot] Circuit help please, low voltage cutout

[Carl Ranson]

Thanks for the replies, i think i understand it now. For some reason I 
though the voltage divider was used to set the reference voltage rather 
just scale the battery voltage so it could be compared with ZD1.

Time to dig out the breadboard.

Chris Hellyar wrote:

>>b. Can Q2 be replaced by a normal transistor and a relay? is the choice
>>of a mosfet because it will use less power than a relay?
>>    
>>
>
>Hi,
>
>last time I reply to this, promise... :-).
>
>Yes, I imagine that is why they used a mosfet, if you just wanted to drive
>a relay with the circuit you could use a Bipolar transistor on the output
>of the opamp to save the cost of the mostfet.  Another BC548 or one of the
>TIP darlingtons for a sledgehammer.
>
>You could also use a resistor & cap in parallel on the relay coil to
>reduce the current drawn by the circuit in operation if you wanted to use
>a relay, but also were concious of current draw.
>
>Cheers, Me.
>
>  
>
>>I know it was mooted that i could do it by using a voltage divider to
>>one of the pics ADC pins etc, but i want it to cover all of the
>>circuitry on the bot (even if the controller is disconnected).
>>
>>I will probably still monitor the voltage into the controller to
>>determine bot behavior but thats a ways off yet.
>>Thanks all,
>>CR
>>
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>>
>>
>>
>>    
>>
>
>
>Cheers, Chris Hellyar
>p: 03 324 4462
>c: 027 255 3494
>w: http://cpix.co.nz
>
>
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>  
>