How can i amplify 1.3mV to 4V dc. Can i use op- ampNTE78A?
I can't find data for part number NTE78A. I find an NTE78, which is a transistor rather than an op-amp.
Looking at your previous posts, it looks like you're trying to interface some kind of output from a radar detector to an Arduino. It also looks like you don't have a whole lot of experience at this.
Can you tell us what model of radar detector you're using, and describe what output you're trying to use? Can you show a link to the radar detector's manual? Maybe we can help you that way.
Sorry i have op- amp nte778. Not nte78. Sorry for the mistake.
I am trying to amplify my output voltage of 1.3mV to about 4V so the arduino can read it.
Is this your radar detector - How to build Economy radar detector (circuit diagram) ?
Yes it is. I have it built already
gives me an output of 1.3mV when it is active
How can i amplify 1.3mV to 4V dc.
That is a total gain of about 3000, which can't be achieved by a single op amp without great difficulty. You need to use two or more op amps, and bandwidth limiting circuitry. Look up "op amp cascade circuits" for some ideas.
Something's wrong...
Are you measuring that 1.3mV with a meter? Are you measuring AC or DC?
1. I'd be very surprised if you can even hear 1.3mV into a piezo.
2. With the 2nd op-amp (the one connected to the piezo) operating open-loop (no feedback) you should be getting nearly 9V peak-to-peak. (Or maybe around 7V... I haven't checked the op-amp's specs.)
That's too much voltage since the Arduino can only safely handle 0 to +5V.
Jellyroll135:
... gives me an output of 1.3mV when it is active
- Where are you measuring 1.3 mV?
- How do you determine when the radar detector is active?
- Do you have some way of illuminating it with microwaves?
- Do you have a piezo device installed?
- If you have a piezo installed, does it sound?
Strange circuit. I wonder if it will be sensitive enough without a special radar detector diode.
If it does work, it will output positive going data or negative going data, depending on the setting of pot R5.
If you set the pot (wiper) to ~4.5-5volt, pin7 will produce positive going data pulses of upto 7volt.
Too much for the Arduino. Use a 10k/10k voltage divider.
-batt to Arduino ground. Divider tap to A-in.
You will have to make the Arduino read AC, not DC.
No experience in that, but I saw recently here an EMF detector sketch.
That might work.
Leo..
Hi,
Just how are you testing the detector?
Tom..... 
DVDdoug:
Something's wrong...Are you measuring that 1.3mV with a meter? Are you measuring AC or DC?
1. I'd be very surprised if you can even hear 1.3mV into a piezo.
2. With the 2nd op-amp (the one connected to the piezo) operating open-loop (no feedback) you should be getting nearly 9V peak-to-peak. (Or maybe around 7V... I haven't checked the op-amp's specs.)
That's too much voltage since the Arduino can only safely handle 0 to +5V.
I fixed my readings. I thought I grounded the atenna but I was wrong. I am now getting 6.5V. My problem now is I am getting to much for the arduino.