[kmziegelbauer]

I have gone over the schematic and was wondering if anyone knew what wattage rating was used on the 15K resistor and if they used a 2n2222 transistor or a n2222 resistor (which is more uncommon)
It says in the pic n2222 but my electrical teacher believes it might be a 2n2222 transistor (which is more common)
maybe a typo?

I am refering to this thread:

http://forum.svrider.com/showthread.php?t=55272

Anyone who has made one or know the specs I am looking for, please help.

 

[DarkMatter]

2n2222a will more than suffice. I'm pretty sure all the resistors used have been 1/2 or 1/4 watt.

 

[kmziegelbauer]

Its a really small resistor (size)?
He believed the 2n2222 was very similar and would handle the job, I will ask if he has a 2n2222a

 

[DarkMatter]

same transistor, just a diff revision. You can buy 2n2222s @ Radio Shack for under $1. You're not dissipating much power through the resistor so heat isn't that much of an issue. Use a 15k 1watt resistor to alleviate any reservations you may have.

 

[kmziegelbauer]

Thanks for the help

 

[DarkMatter]

no prob. I posted a link to the transistor datasheet in the other TRE thread.

 

[kmziegelbauer]

that is a good idea, more info in one place

 

[super32]

same transistor, just a diff revision. You can buy 2n2222s @ Radio Shack for under $1. You're not dissipating much power through the resistor so heat isn't that much of an issue. Use a 15k 1watt resistor to alleviate any reservations you may have.

So something interesting I want to bring up.
I purchased my transistors from RadioShack in a package deal. Specifically, I got this from RadioShack

So this pack comes with

• 5x 2N2222 transistors
• 5x 2N3904 transistors
• 5x 2N4401 transistors

Yeah, there are 15 total transistors in this package. But, that's all I could find in the store with n2222 transistor type. Anyway, the RadioShack package says that all 3 types are "general purpose" transistors.

I tried to do a highlevel comparison between these 3 transistors (comparing datasheets), and there doens't seem to be any particular differences. At least, nothing I could see. There was a bit of difference in delays, but that was in the millisecond range. I'm not sure if theres anything we're doing that requires any higher resolution than ms range?

So, question is... would the n3904 and n4401 work? I may try to fab one up this weekend with the extra OEM pins I have and see how it works. I doubt there'd be any difference, but even if there were, it'd probably be small enough to go unnoticed.

Other's inputs/opinions/concerns?

 

[kmziegelbauer]

Are you saying it would work faster with the n3904 or n4401? But only milliseconds faster?

As long as they are within the original specs i dont believe it would be a problem.

I just purchased the same set of transistors from radio shack.

Did you get 1/2 watt resistor? That is what I was going to make mine with.

Let me know your setup and if it works well and I will make it the same way.

 

[super32]

Are you saying it would work faster with the n3904 or n4401? But only milliseconds faster?

As long as they are within the original specs i dont believe it would be a problem.

I just purchased the same set of transistors from radio shack.

Did you get 1/2 watt resistor? That is what I was going to make mine with.

Let me know your setup and if it works well and I will make it the same way.

well, the n2222 is faster than both of the n3904 & n4401. So, if I were to use the n3904 or the n4401, the 'switching" might be a little delayed, but in the order of ms.

IIRC, I used 1/4W resistors found at Fry's Electronics.
But, like it was said earlier, I believe the 1/2W resistors would work just as fine. The resistors are handling "signals" rather than big voltages or anything. So the amount of power/heat dissipation given by the resistor will certainly be insignificant to the functionality/precision of the resistor.

When I get home (Saturday) I'll confirm the 1/4W resistors.

Or if I read your question incorrectly...
I already made my aTRE. I used the n2222 and the supposed 1/4W resistors as given in the instructions from the other thread.

 

[DarkMatter]

Any general purpose NPN switching transistor with a fast turn on/off time and an appropriate VCBE rating will work just fine. You're not sourcing or sinking very much current, and you're really just using the transistor as a switch.

 

[kmziegelbauer]

Finished my final product. Shink tubing was put over all components to ensure no moisture gets in. Will be installing it tomorrow.

 

[super32]

Finished my final product. Shink tubing was put over all components to ensure no moisture gets in. Will be installing it tomorrow.

enjoy!
I guess I should have mentioned that you could use black-RTV sealant that would help with the "weather-proofing". I squirted some inside the shrink tube prior to heating it up to shrink it. Thus, when the black RTV dries up, it'll form a heat-resistant barrier around the solder points and the transistor itself.