EMF Probe Project

Ron H

Joined Apr 14, 2005
7,014
The drawing you posted is a layout (not a schematic). I'm gonna need a schematic that matches the layout (with correct IC pin numbers).
 

Thread Starter

Butterworth

Joined May 6, 2009
135
Hey Ron, here you go!

As I had mentioned in the last post, I switched op-amps 2 & 3 with eachother and left amps 1 & 4 alone, as well as Q1.

I got rid of the ground & power loops, instead I used multiple posts to hook up the power and ground. My thought was to minimize the length of the traces but have wiring connected to 2 spots for each. This also helped with placement of other traces as it left me with more room to play with.

Thanks again, I look forward to hearing your input!
 

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Ron H

Joined Apr 14, 2005
7,014
Hey Ron, here you go!

As I had mentioned in the last post, I switched op-amps 2 & 3 with eachother and left amps 1 & 4 alone, as well as Q1.

I got rid of the ground & power loops, instead I used multiple posts to hook up the power and ground. My thought was to minimize the length of the traces but have wiring connected to 2 spots for each. This also helped with placement of other traces as it left me with more room to play with.

Thanks again, I look forward to hearing your input!
It looks good! You mentioned 2 wires for each battery terminal, but I only see one connection for the negative battery wire (GND), which you labeled 9V-. This is good.
 

Thread Starter

Butterworth

Joined May 6, 2009
135
It looks good! You mentioned 2 wires for each battery terminal, but I only see one connection for the negative battery wire (GND), which you labeled 9V-. This is good.
Ha, you know what... between the many revisions this pcb has gone through, I am getting them mixed up. I only had the one set of leads from 9V+/- on that pcb.

I am very glad to hear that it looks good! I do feel confident that not only will this smaller board be the final product, but it will also help out the space issue I have in my project box!

One major thing I am iffy on though, can I use standard wiring from the mechanical switches / meter etc, to connect to the board? or shouldstick to the shielded wiring?
 

Ron H

Joined Apr 14, 2005
7,014
The signal wiring is no more than 6 inches @ worst case... but I can make them shorter. Power wiring is about the same.
I would use a shielded wire for the probe. See attachment.

The other connections should be OK with insulated wires, so long as you keep them well away from the probe input.
 

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Thread Starter

Butterworth

Joined May 6, 2009
135
I would use a shielded wire for the probe. See attachment.

The other connections should be OK with insulated wires, so long as you keep them well away from the probe input.
I like that pic, it looks like audio cable from say a 3.5 mono patch cord? I have some of this laying around, so I think it will do well. I will try to keep the board as low as possible in the project box to maximize distance from the probe input jack.

Another thought:
If I were to use this circuit in low lighting situations, my panel meter doesn't light up (unfortunately) so I was considering using an 8-led sequence ranging from 1-4 (green), 5-6 (yellow) & 7-8 (red), similar to a VU meter if you will. The only thing I can't wrap my head around is, can I tap into my meter input to send a signal to the led driving circuit? If so, the voltages will be sufficient? I found a sample circuit on the web for a VU meter, could this possibly work?
 

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Ron H

Joined Apr 14, 2005
7,014
I like that pic, it looks like audio cable from say a 3.5 mono patch cord? I have some of this laying around, so I think it will do well. I will try to keep the board as low as possible in the project box to maximize distance from the probe input jack.
That should work.

Another thought:
If I were to use this circuit in low lighting situations, my panel meter doesn't light up (unfortunately) so I was considering using an 8-led sequence ranging from 1-4 (green), 5-6 (yellow) & 7-8 (red), similar to a VU meter if you will. The only thing I can't wrap my head around is, can I tap into my meter input to send a signal to the led driving circuit? If so, the voltages will be sufficient? I found a sample circuit on the web for a VU meter, could this possibly work?
You should probably open a new thread for this so that everyone will see it. I have a suspicion that most people have unsubscribed to this thread. No one else has posted since June 10, and even then, there were only two other members contributing.
Having said that, have you considered LM3914, LM3915, or LM3916?
 

Thread Starter

Butterworth

Joined May 6, 2009
135
That should work.

You should probably open a new thread for this so that everyone will see it. I have a suspicion that most people have unsubscribed to this thread. No one else has posted since June 10, and even then, there were only two other members contributing.
Having said that, have you considered LM3914, LM3915, or LM3916?
This is true, I may make a new thread once this base project is up and running! But no, I haven't considered anything other than that schematic, because I didn't know if would integrate well or not. What is the difference b/w the LM324 and the ones mentioned above?
 
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