Schematic Symbol Help? (SuperSID)

[mishima]

Hi, can anyone help me identify the big blue boxes' schematic symbol? The actual physical component sort of looks like a small inductor or oscillator.

SuperSID Schematic

The purpose of this circuit is to be a preamplifier for VLF signals related to ionospheric disturbances, I believe.

 

[FOIWATER]

It's the symbol for a varistor, I assume it's for attenuating (resistor) transients and shunting (the varistor) transients. A surge protecting device?

My best guess, might not be correct though

 

[mishima]

Ok, that actually makes sense, the antenna I have connected will get big spikes from CRT monitors and even fluorescent lights if close enough. Probably some other stuff can cause bigger problems.

 

[dlgoff]

Well, this is a thermistor.

http://electronicsclub.info/symbols/therm.gif

image compliments of http://electronicsclub.info/circuitsymbols.htm

 

[mishima]

Hmm, ok...so its kind of like a reusable fuse here? Like it opens a path to ground if current (thus temperature) gets to high? Sorry, I don't know much about electronics.

 

[dlgoff]

Hmm, ok...so its kind of like a reusable fuse here? Like it opens a path to ground if current (thus temperature) gets to high? Sorry, I don't know much about electronics.

I don't know what the A inputs are, but it looks like it's used as a temperature sensor to adjust for temperatures differences. (varying temperatures outdoors perhaps?)

From the http://en.wikipedia.org/wiki/Thermistor link.

A thermistor is a type of resistor whose resistance varies significantly with temperature, more so than in standard resistors. ... Thermistors are widely used as inrush current limiters, temperature sensors, self-resetting overcurrent protectors, and self-regulating heating elements.

 

[mishima]

The A's are the antenna connections. It's a 1m "small loop" (primarily detects magnetic component of EM radiation) antenna suitable for detecting the transmitted VLF radio signals that are part of submarine communication networks.

The idea is that when a solar flare occurs, the ionosphere is disturbed which also disturbs this network. SID is sudden ionospheric disturbance; this is the second (super) version of a circuit developed by Stanford for mass distribution to high schools for the purpose of space weather education.

 

[dlgoff]

The A's are the antenna connections. It's a 1m "small loop" (primarily detects magnetic component of EM radiation) antenna suitable for detecting the transmitted VLF radio signals that are part of submarine communication networks.

The idea is that when a solar flare occurs, the ionosphere is disturbed which also disturbs this network. SID is sudden ionospheric disturbance; this is the second (super) version of a circuit developed by Stanford for mass distribution to high schools for the purpose of space weather education.

Outstanding. What a fun way to learn. :thumbs:

 

[mishima]

Yes they had a lot of fun building the antenna and seeing the response of fluorescent lights and a CRT tv, and trying to find the VLF stations. I just wish I knew more about the circuit so I could I could explain it to them, heh. I understand at a basic level the circuit is just a preamp, and understand opamps somewhat, but that is about it.

 

[jim hardy]

They're clearly surge suppressors, one for normal mode and one common mode.

A 1 m^2 loop doesn't sound big, but nearby lightning strokes generate substantial electro-magnetic fields.
I once returned from a vacation to find in my garage:

In my FM receiver two capacitor-looking devices that coupled the antenna leads were blown apart; they might have been suppressors I don't know for the receiver still worked but sensitivity was degraded.

My two magnetic compasses that i kept near the workbench had got their needles re-magnetized so the red ends pointed south instead of north.

I suspect this circuit designer has a similar experience under his belt...

 

[dlgoff]

Thanks for the correction Jim.