Geofex Spyder x2

[dream_noir]

So I figure I'll have some way of getting a hold of the transformer for it, I might as well ask the rest of the questions I have about it.

120V AC input, I'd fuse then switch it on the hot wire, correct? Does a 10amp fuse sound right? From there it goes into the transformer, simple enough. The secondaries then go into the rectifier. With some research into past topics on the spyder I could find it on mouser, but does small bear carry the correct part? If not, can anyone give me some more information on it, beyond the part number DB01 so I can see if any of the local shops stock it. Small bear stocks the voltage regulator, so if I end up building this I can get that there, not a problem. Capacitors confuse me though. I'm assuming from the diagram that they are polarized (or whatever the special word for having a positive/negative terminal is)? I understand the values, but I have no idea what type of caps are polarized and which ones aren't. What should I be looking for in regards to them? At the end the negative lead goes to the pin and the positive goes to the ring on boss style jacks, right? Also, to have an indicator LED, I would just run it in parallel off one of the 9v jacks with a resistor, right?

A few more questions that are a bit more out there, I don't have to run anything off all the secondaries right away do I? Like, if I built it with the 8 9vDC outs but left the 9vAC out with its wires taped off would that be fine? Last (I think) if I wanted an 18V output instead of 2 9V outputs, how would I do it? I know you run them in series, and I understand how it works with say, a battery, but I have no idea in this case. That's all I can think of for now, if I manage to put this together, it'll be my first real DIY from scratch (although I'm comfortable working with 120V AC, I've done quite a bit of house wiring).

[R.G.]

I'm comfortable working with 120V AC, I've done quite a bit of house wiring

OK. I'll assume that you are skilled in the art then.

120V AC input, I'd fuse then switch it on the hot wire, correct?

Yes. I personally don't do AC line ins without using an IEC receptacle. I hate the other methods of strain relief.

From there it goes into the transformer, simple enough.

Important point: if you put it in a metal box, the safety ground goes to the metal box.

The secondaries then go into the rectifier. With some research into past topics on the spyder I could find it on mouser, but does small bear carry the correct part? If not, can anyone give me some more information on it, beyond the part number DB01 so I can see if any of the local shops stock it.

Any diode bridge of 1A current rating or more works, as does a set of four 1N4004 diodes connected up in a bridge.

Capacitors confuse me though. I'm assuming from the diagram that they are polarized (or whatever the special word for having a positive/negative terminal is)? I understand the values, but I have no idea what type of caps are polarized and which ones aren't. What should I be looking for in regards to them?

You want aluminum electrolytic capacitors. The capacitors will come with markings on the + terminal, or the - terminal, or both, for the right way to connect them. Sure enough, the + terminal goes to the end of the bridge rectifier that produces a + voltage compares to the other terminal, the - terminal to the end that makes a - voltage compared to the + terminal. You want capacitors rated at 25Vdc or more. The more capacitance and voltage, the bigger the cap.

At the end the negative lead goes to the pin and the positive goes to the ring on boss style jacks, right?

Yes. It's important that neither side contacts the metal enclosure.

Also, to have an indicator LED, I would just run it in parallel off one of the 9v jacks with a resistor, right?

An LED in series with a current limiting resistor of 2K  to 10K can go in parallel with one of the 9V jacks, yes. If you don't put in the limiting resistor, the LED burns up.

I don't have to run anything off all the secondaries right away do I? Like, if I built it with the 8 9vDC outs but left the 9vAC out with its wires taped off would that be fine?

That would be fine. They don't have to be loaded.

Last (I think) if I wanted an 18V output instead of 2 9V outputs, how would I do it? I know you run them in series, and I understand how it works with say, a battery, but I have no idea in this case.

If it's a temporary connection, yes, you can just hook two in series. If you want a permanent 18V outlet, it's better to hook two transformer secondaries in series to get a bigger voltage, run that into ONE diode bridge and ONE filter capacitor (that itself now has a higher voltage rating) and then regulate the output with ONE 7818 three terminal regulator. This setup avoids some potential problems with series connections of lower voltage regulators.

[dream_noir]

Well I wouldn't say skilled, but I think I can avoid killing myself. Thanks for all the info btw, the only thing I still don't 100% get is the diode bridge, but Ive just never heard of it before. Thanks again!

[R.G.]

A diode is a device like a one-way water valve. It only lets current flow one direction, that being the direction the arrow points.

A diode bridge is set up so that when the AC on the transformer secondary winding is in one direction, two of the four diodes in the bridge let the + side connect to the + end of the cap and the - side of the secondary connect to the - side of the cap. When the polarity of the secondary inverts, the other two diodes are set up to connect the reversed winding to the + and - sides of the cap correctly. You need two diodes for each wire from the secondary, because each wire from the secondary will be alternately the most positive lead and the most negative lead. The two diodes let it push current into the + side of the cap and pull current from the - side of the cap as the voltage inverts.

Single package diode bridges are just four diodes hooked up the right way and blobbed with epoxy into one package.