Just need some help in identifying a popular semiconductor package(preferably NTE) to drive a 12V relay (approx 200mA) from a very low current +12V input
It mostly depends on your requirements. The 12V relay is good information, we can assume a mx spike voltage. Is the 200 mA what the relay will drive? That is not relevent except to guess at the drive requirement. Is the catch diode part of the relay itself or will be providing that in your circuit? What packaging, surface mount? What temp. range? What are you driving this from? Is it a typical ground connection or do you need to high side drive the relay coil?
A generic answer would be something like the venerable 2N2222. Since you want to buy from NTE, that would be a good place to start. If you are just building one, a catalouge shop cross reference should be OK. The IRF type FET's with logic drive might be easier for you and not cost much more, it depends on your sensitivity of NRE to production part costs.
I guess I didn't provide enough information. Actually I want to add an electric fan on the radiator of the diesel engine for a standby generator, The controls use 12V power and I want to switch the fan on after the engine begins running. The "engine running" lamp is controlled by an auto-start module which provides a +12v output after the engine has successfully started. I simply want to connect on this output (which operates the lamp) some sort of a buffer/driver which will pull say a couple mA and in-turn operate a relay coil demanding 12V at approx 200 mA. Of course this driver will have to be mounted somehow on the generator in its control box. Closure of the relay contacts will operate the fan. Hope this makes it clearer.
Thnaks
If the +12V is really just a well regulated 12V then this might be your easiest route. By using a device that has taken cae of most of the problems, you won't have to sory about them.
This if for an ON semi automotive version NUD3124.
If the 12 V is realy a ra 12 V with glitches and noise and large swings in voltage from charging and EMF during operation, you might have to take some other precautions.
If this is a one-off why aren't you just using a mechanically stout regular screw terminal solid state relay? They take in 4 to 32Vdc at about 10mA and they can switch up to 40 amps! Pitch your mechanical relay and stick one of these in.
Drive it directly. If you must use your existing relay just use the smallest one to switch It. This gets you robust screw terminals and mounting holes that are fit for mounting on or around engines using ring connectors.
I want to thank you both very much for your suggestions. I will try to see if any of the products suggested can be sourced here; I am in Jamaica. Thanks again
200 mA is enough to drive almost any transistor with
reasonable beta. Suggested:
NTE196/331 = TIP41
NTE181 = 2N3055
NTE261 = TIP125
Any of the above (and scads more) should be suitable.
If the base current becomes a problem, use a 2N3053 or
3054 (progressively larger), or in extreme cases, use
a 2N2222 (as suggested) or 2N4401.
You can look up the NTE equivalents yourself; they have
a cross-reference page.
<als>
