Impulse 2

[qute1]

Any further developments on the impulse2 i can't for the life of me see why this thing is not better it should really be far more sensitive than it is (better depth anyhow) and i am at a loss as to how to improve matters on paper it rocks but in reality it sucks feet......?

[BC547]

The scope is triggered off channel 2 which is monitoring the TX pulse width from the PIC (pin 10), and channel 1 is the signal at point D. As you can see, the signal just comes out of saturation at about 50us.

Forgive me my opamp ignorance, but how can the signal at point D = after attenuation 10:1 have an amplitude of 1.76 V when the opamp is powered by VDD = 5V ?
Even 12V / 11.1 * 1.1 = 1.18 ?
On the schematic, "VDD" is the output of the 78L05 ?
I assume the opamp is powered by 12V instead of 5V?

Thanks,
- Bernard

[qute1]

Nice one!

[dbanner]

Ok, the UT2 is audio driver transistor 1HW57 is BC857. NPN general purpose transistor, surface mount. Here is the datasheet for several which includes the 1HW57/BC857. SOT-23, SOT-323 package.
1HW is SMD code, I found datasheet here:http://www.s-manuals.com/smd/1h

[dbanner]

transistor is marked 1 HW 57 if that helps?

Hey thanks for reply! I'll try to find a datasheet.

[qute1]

transistor is marked 1 HW 57 if that helps?

[dbanner]

Digital mode, audio driver transistor?
Can anyone shed some light on this peculiar output?

[dbanner]

What transistor is the audio driver(UT2). Does it have internal resistors? Or is it just ordinary NPN transistor? And what is the purpose of C5?
Thanks

[dbanner]

I've looked at the layout again, and it does seem to be correct.
Perhaps someone else with an Impulse PI can double-check.

[BC547]

Thanks for measuring it and explaining the functionality, George !
I like the front-end simplicity of this design.

One of the major advantages of direct sampling with the internal 10-bit ADC is that you can accumulate samples over time.
Something that can not be achieved easily with pure HW, I assume.
This is what I do in the Pickini design anyway: the sensitivity pot setting determines how may samples are added to come to a final value ( keeping in mind the pulse frequency as limiting factor : too many pulses accumulated would slow down the final result...)
If only I had more time I could easily make this work with a couple of potmeters for pulse width/frequency, delay, sensitivity,.. - without the push buttons and display.

Thanks again,
- Bernard

[Qiaozhi]

Has anyone built this circuit already ?
If so, can you post a picture of the signal at label "D" = PIC signal input ?

Thanks,
- Bernard

I don't know what you're expecting to see there, but it's not very exciting. Much as expected.
The scope is triggered off channel 2 which is monitoring the TX pulse width from the PIC (pin 10), and channel 1 is the signal at point D. As you can see, the signal just comes out of saturation at about 50us.

By the way, there's no need to build this circuit, as you can buy it ready-made from the seller at a good price. You'll have a problem with the code anyway if you build it yourself, as it's not available.

Unfortunately this little circuit has started to play up, as the LCD display sometimes does not display anything or gets corrupted. As far as I can see, the problem is with the SIL connector. If you were going to put this circuit in an enclosure, I would recommend connecting the display with some ribbon cable for reliability.

[BC547]

Has anyone built this circuit already ?
If so, can you post a picture of the signal at label "D" = PIC signal input ?

Thanks,
- Bernard

[BC547]

I am not an analog expert, but the amplifier section (U1) looks interesting:

- DC coupled
- U1b : x1000 ?
- U1a : x24 ?
- and at the output of U1a : attenuation 10:1.1 to make the signal acceptable for the PIC ADC range 0...5V.


I would be very interested in a scope picture of the signal at label D = PIC signal input.
I assume if the signal is amplified x24 and then attenuated 10:1, the amplifier might as well be x2.4 without attenuator ?

[Qiaozhi]

did you try to check on closing pin-to-pin by tester?

Yes. I did a continuity test between the pins. As far as I can tell, the schematic is correct.

[kt315]

did you try to check on closing pin-to-pin by tester?