Replies to Minipulse Plus

[Davor]

Yes, this seem a 4017 problem. It is not resetting properly. See what happens at pin11 of 4017. Also see if 4017 receives a reset pulse at pin15 or not.
The circuit works as follows... 4017 keeps pin11 high (from the previous cycle) which prevents the oscillator from oscillating. The falling edge of 555 output creates a short reset pulse that puts all 4017 outputs low, and hence enables the oscillator to start oscillation. The first oscillator pulse duration is adjustable relative to the oscillator period, hence GB adjustment. 4017 counts 9 pulses until the pin11 goes high again and stops oscillation. When 555 output goes low everything starts all over.

There is a way to optimise pulse rate in a way that no time is lost after EF pulse until Tx charge starts, and hence improve the SNR of a whole rig. I'll try that.

[6666]

Hi Davor, somewhere between your GB sim and the schematic drawn by Sinclairuser some of the values on the reset line have changed from 220p 10k and 10k
to 47p 22k and 22k with these new values I only get .5 volt positive and just barely 1 volt negative is this voltage enough to trigger the 4011 gate ?
http://s15.postimg.org/k5y25w5y3/reset_pulse_4011.jpg

[6666]

I've been experimenting with the values from the Sinclairuser schematic in your gb sim
if you add the extra 10k which is R4 in the MPP in series with the 47pf and 22k and 22k the reset pulse from the 4011 just flat lines and stops working
if you up the value of the 47pf cap to about 100-150 pF in the sim, then the 4011 gate starts to trigger correctly, will try this tomorrow in real circuit.

[Davor]

Makes sense. I did not pay much attention to these values, I assumed 47pF -22k should be OK, but surely the CMOS input capacitance will limit the spikes and even disable resetting function if resistances are too high and a coupling capacitance too low.
I introduced 47p 22k values in a schematic "Cor 2" in post #416 and ... did not test it. My bad.

Nice catch

[6666]

My apologies to Sinclairuser, it was the schematic drawn by Silver dollar post #501.

[6666]

After doing some bench testing the toggle point for a 4011 with a supply voltage of 4.67 volts is about 2.15 volts.

[6666]

Hi Davor, I have some good news, back later.

[Davor]

Nice to hear that

[6666]

This little video shows the 555 TX pulse at top and the out put pulses from the 4017, initially you see the first sample and EF pulses
then by joining all outputs together you see the GB pulses added.
BTW this is the 4093 circuit.
https://www.youtube.com/watch?v=DKhV...ature=youtu.be

[Davor]

Nice
I still believe 4011 will perform more predictable.

[scrungy_doolittle]

In a way that is the basic idea of adding another counter. You can't use D0 on a second counter because it is the same as D9 on a first one (or D8 in your attachment). Once I sort out some hiccups at work I'll see to the GB circuit.
There are other ways to realise this circuit, but I prefer 4017 as it enables combining various timings in wired OR style.

said like a true hardware geek why not just use a small 16 pin pic and then you can have anykind of counter you want

[6666]

said like a true hardware geek why not just use a small 16 pin pic and then you can have anykind of counter you want

Well teach us how to do it thanks

[6666]

Hi Qiaozhi

if you dont mind I have a hypothetical question for you about the preamp in the MPP, I'm working on another project
and the preamp would be handy, the question is , seeing that the preamp is AC coupled and does not have any offset
adjustments , do you strictly have to supply regulated + and - 5 volts to it, could you simply use
just two 9 volt batteries ?

[Davor]

said like a true hardware geek why not just use a small 16 pin pic and then you can have anykind of counter you want

I can't convince a pic, or any other micro for that matter, to provide a continuously variable delay in a 10us range. I gave already a slightly different solution for this problem using a micro that varies a different delay which is not this tight. So far I'm not that much interested in micros.

[Qiaozhi]

Hi Qiaozhi

if you dont mind I have a hypothetical question for you about the preamp in the MPP, I'm working on another project
and the preamp would be handy, the question is , seeing that the preamp is AC coupled and does not have any offset
adjustments , do you strictly have to supply regulated + and - 5 volts to it, could you simply use
just two 9 volt batteries ?

Since the preamp output is ac-coupled to the next stage, any dc-offset is effectively removed. Therefore I would expect it to work with two 9V batteries.