Old 04-24-2012, 12:33 AM #49
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Default Re: Help With Ophir Head and Panel Meter-1 Battery

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Originally Posted by Benm View Post
Just do a parametric search on a manufacturers website (nxp, national semicondictor etc) to find a suitable transistor. I presume you do not need an exact equivalent, just something that meets or exceeds the specifications of the 437 and 438?
The challenge is (frankly) that I'm using these in a circuit designed by Jib, not by myself. So I'm not clear on what meeting or exceeding specifications means in this case (or more accurately, which specifications even NEED to be met).

The 437 is a remarkably beefy transistor for driving an Ophir with such low current consumption. Hence me wanting to replace them with surface mount parts. That said, I'm not clear on whether the parts I chose will for some reason not be appropriate.


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Old 04-24-2012, 01:02 AM #50
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Default Re: Help With Ophir Head and Panel Meter-1 Battery

Quote:
Originally Posted by rhd View Post
The challenge is (frankly) that I'm using these in a circuit designed by Jib, not by myself. So I'm not clear on what meeting or exceeding specifications means in this case (or more accurately, which specifications even NEED to be met).

The 437 is a remarkably beefy transistor for driving an Ophir with such low current consumption. Hence me wanting to replace them with surface mount parts. That said, I'm not clear on whether the parts I chose will for some reason not be appropriate.
The BD437 and BD438 are standard NPN and PNP silicone transistors
respectively that can handle up to 4 Amps of current.
Any standard silicone surface mount transistors that can handle 500mA
to 1Amp at double the voltage they will see should work fine in that Jib
circuit.


Jerry
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Old 04-24-2012, 01:09 AM #51
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Default Re: Help With Ophir Head and Panel Meter-1 Battery

Quote:
Originally Posted by rhd View Post
The challenge is (frankly) that I'm using these in a circuit designed by Jib, not by myself. So I'm not clear on what meeting or exceeding specifications means in this case (or more accurately, which specifications even NEED to be met).

The 437 is a remarkably beefy transistor for driving an Ophir with such low current consumption. Hence me wanting to replace them with surface mount parts. That said, I'm not clear on whether the parts I chose will for some reason not be appropriate.
I would imagine you could replace them with a common MMBT2222A and its compliment (PMBT2907A). The ophir only needs what, a few 10's of ma? Seems like he originally designed that board for some heavy loads.

Edit: Oh, didnt see your post Jerry

Last edited by benmwv; 04-24-2012 at 01:14 AM.
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Old 04-24-2012, 01:40 AM #52
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Default Re: Help With Ophir Head and Panel Meter-1 Battery

Hey,

Thanks guys, very much appreciate the help

I've also taken the step of swapping the large 680uF aluminum capacitors for 470uF Tantalum surface mount parts. They're 10V which makes me a bit nervous as each rail is getting 6V, but I think that's enough clearance given that I'm regulating the circuit's input to a steady 12V (which is what gets split).

Any thoughts on the move from 680 to 470? (keeping in mind that it's also a move from aluminum to tantalum.
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- Federal Aviation Administration - Laser Safety Initiative (link)
- Info release from Laserglow - Default Canadian restrictions on portable lasers (link)
- The Necessity of Safety Goggles (link)

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