my first PI detector

[kt315]

I just received the NH-173 kit from new hobby

unknown kit for the forum. can you share a schematic of it?

[Carl-NC]

I would like to try modifications but would like your opinion

Opinion on what?

[ducran_lapoigne]

Is this likely to improve operation?

[MDfanatic]

Can you post some information about your coil? Like coil size, how many turns, wire diameter etc so we can start from somewhere.
The coil is the most important factor and the first thing to check if the detector is not working as it should.

[Carl-NC]

Oh, I see now. You want to replace the single 555 timer circuit with the dual 556 timer circuit. The dual looks like it has independently adjustable frequency and pulse width (I assume) which are useful additions in a PI design. You can then vary them to see how performance changes.

However, this design uses a simple threshold detector instead of the usual sampling integrator so pulse frequency won't have much of an effect. Probably that should be your next step.

[GeoMax]

Hi ducran_lapoigne,

why do you want to use the dual 555 timer circuit from the Delta Pulse detector on a Pirate circuit? There is no benefit for it. Changing the frequency for example does not make sense on the Pirate PI, because it was originally designed to work for frequencies of around 150 Hz only. It would only make sense to have an additional pulse width adjustment. For this to achieve, you do not need a double 555 timer. Just add to the existing 555 timer circuit a pulse width adjustment.

[GeoMax]

Hi ducran_lapoigne,

just add to your 555 timer for example the highlighted circuit part below. This changes the pulse width output of your 555 timer as well. The diodes are standard 1N4148. The potentiometer can be anything between 20 to 100k.

[boilcoil]

It is not necessary to add new 555, it has to use only scheme in GeoMax's post and change R1 with potentiometer.
Adjust freq by pot R1, and duty cycle (delay of sample) by RV1.