[ATM] device controllers

[Mike Lockwood]

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.