From: firstname.lastname@example.org (Robert Richter)
Subject: Re: How to get CMOS counter to drive a relay?
Date: 13 Oct 2002 19:50:56 -0700
NNTP-Posting-Date: 14 Oct 2002 02:50:57 GMT
"Justin Farrelly" wrote in message news:...
> One of the easiest ways IMHO is to use a FET on the output, in the ground
> side of the relay you mention. It will need to have a Vgs(thresh) of about
> 1.5 to 2.5V. You might want to look at Vishay (www.vishay.com) and use the
> online selector guide, but something like a TN2460L should do the trick.
> Fets are voltage devices, not current devices (like transistors) making life
> a lot easier. Make sure the total energy is not greater than the protection
> diode rating or FET rating - but other than that your Q output strait to the
> gate, relay high side to +V, relay low side to drain of yout N channel FET,
> ground to source, and away you go!
> This FET should be fine, is available as a TO92, and worth about USD$0.50.
> Hope this helps.
> "DaveC" wrote in message
> > What's the simplest method to get a Fairchild CD4020/40/60 counter to
> drive a
> > relay with one of its Qx outputs? Is simply driving a transistor to drive
> > relay OK?
> > Data sheet says output is low-power TTL compatible: fan-out 2x for 74L or
> > for 74LS.
> > The relay coil is 12v dc, 720-ohm, 16.70 mA (Omron G6B-2114P) used to
> > a 150 mA(?), 30vac HVAC control circuit.
> > Please give component p/n's and values.
> > --
> > Note that my return address is corrupted in an attempt to reduce spam. If
> > choose to e-mail me, please correct my address as described below.
> > Thanks,
> > Dave
If you are interested in more than one ouptut, I would recommend the
LM2803 which is a relay driver chip; it can handle eight relays from
TTL or CMOS inputs.