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Re: [ATM] device controllers
I'm not sure that an 8 pin PIC wouldn't be as cheap as a 555 and a
capacitor; it really depends if you are more comfortable messing with
hardware or software.
I did a dew heater controller with a 555 and a TIP530 MOSFET and IIRC I
just connected the 555 output to the FET gate. I've also done a dome
controller where a TIP530 is driven by an RS232 output line from a PC
and switches a 12V windscreen wiper motor. These MOSFETs seem pretty
bullet proof, they switch with about 5V and almost no current and have a
built in diode that seems to cope with inductive loads pretty well.
Chris
Mike Lockwood wrote:
> Hi,
>
> Dominic-Luc Webb wrote:
>> Not sure about easily. I have had some major adventures getting
>> 555 timers to drive transistors. On the other hand, I have an
>> excellent PMT power supply that can give pulses to a HV relay
>> that works great. There are plenty of cheap/simple 2 transistor
>> circuits out there that can do this as well.
>
> Hmmmm.... a 555 should produce an output voltage close to the supply
> voltage when it's output is "on", and that should easily drive a
> MOSFET into full-on mode. (MOSFETS are voltage-controlled,
> transistors are current-controlled.) If you want to avoid that, have
> the 555 drive a high-current buffer into saturation and the buffer
> should be able to drive the relay with no problem. Surely there are
> lots of circuits online.
>
> You should be able to set up the first 555 circuit to pulse every
> minute or so. Then that pulse should also be able to activate another
> 555 circuit that would turn on the grit dispenser for a chosen number
> of seconds, after which it turns off. The intervals might be a bit
> temperature dependent, but I doubt it would be a problem.
>
> Just Google "555 timer circuit" and start looking through the 437,000
> hits.
>
> Mike L.
>
>
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>
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