trimmer size?

[grungymike]

I'm getting ready to start building a Hammerhead I. I've done preliminary
component research, started laying out a PCB (existing pattern won't fit
selected housing). What I'm wondering about is the power rating for the trmmer pots on the board. I figured on 1 watt cermet pots on the case for the stuff I expect to fiddle with regularly (threshold, gain, delay#1 & 2), and 1/2w cermet trimmers on the board for the rest of 'em. Is 1/2w big enough or am I risking burning out the sliders?

thanx

gm

[Molzar]

Mike,

The 1/2 watt trimmers have plenty of overhead. The case pots don't disapate much power either. I use inexpensive carbon 0.2 watts, these work fine. Larger pots might be wirewound design and add inductance, although I'm uncertain if this would have any negative affects.

The only parts that get warm as I recall are the damping resistor, and the MOSFET depending on your settings. I use 1/2 watt on the damping resistor.

Also sounds like your planning on laying this out on your own "custom" PCB just to get it to fit in a perticular enclosure. To me this sounds like a lot of extra work, much easier to use existing pcb (Carl's) and find a sutable enclose for it. This also has the advantage of using a proven pcb, that most here could help with any problems.

But different people have different goals and talents for this hobby so you don't have to listen to me, just my 2 cents.

Also when ordering the trimmers make sure your adjustment access is correct (for the pcb used) as these come in several styles (orientations).

Good Luck,

Molzar

[grungymike]

layout...

Yeah, it is a lot of extra work, but some years ago I earned my raisin pie designing multilayer CMOS and TTL circuit boards for mil spec applications. Besides, the thru hole boards aren't available anymore, and I don't trust surface mount stuff for field use. In my opinion, surface mount boards just aren't robust enough, won't take the banging that happens when you slide off a hillside, bounce off of a rock, and drop your detector in the gully you just landed in.

What's been the real skullcracker has been learning what all those itty bitty parts on the board actually do. The article that accompanies the Hammerhead schematic got me started studying analog circuitry, something I thought I'd never be interested in. No wonder I wear eyeglasses with coke bottle lenses...

As for yer two cents, it's worth more than gold to me. Thanks for the input!!!

gm