From: "Justin Farrelly"
Subject: Re: How to get CMOS counter to drive a relay?
Date: Sun, 13 Oct 2002 17:59:35 +0000 (UTC)
Organization: BT Openworld
NNTP-Posting-Date: Sun, 13 Oct 2002 17:59:35 +0000 (UTC)
X-Newsreader: Microsoft Outlook Express 6.00.2720.3000
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
> 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.
> Dave Carpenter
> Sound Logic
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