PI-1 oddities

[raygdunn]

Hi,

Another beginner breaks cover...

I recently completed the book and found it superb to fill in the background knowledge needed to debug a planned kit build.

Whilst breadboarding the PI-1 circuit Fig. 12-8. I noted that IC4a pins 5 and 12 should I believe read 13 and 4 respectively, as per the monostable diagram on the previous page. As (in error) they duplicate IC4b, it is fairly obvious, so no real problem. This isn't currently listed in the Errata.

I also have managed to cook three chips, that I used for that monostable. The diagram says 74HC221and I actually used CD74HC221E, which appears suitably compatible. At least two were after raising the test voltage to 12V, with a view to using something more potent than the design PP3. (A note on preceding page says PI-1 only should be OK to 12V)

Checking the specs of this chip, it's rated for 2-6V, so I'm thinking it copes with 9V, but gets dodgy by 12V. There must have been quite a few builds of this circuit over the past couple of years, so must be OK at 9V, I would think.

Ray

[Qiaozhi]

Hi,

Another beginner breaks cover...

I recently completed the book and found it superb to fill in the background knowledge needed to debug a planned kit build.

Whilst breadboarding the PI-1 circuit Fig. 12-8. I noted that IC4a pins 5 and 12 should I believe read 13 and 4 respectively, as per the monostable diagram on the previous page. As (in error) they duplicate IC4b, it is fairly obvious, so no real problem. This isn't currently listed in the Errata.

I also have managed to cook three chips, that I used for that monostable. The diagram says 74HC221and I actually used CD74HC221E, which appears suitably compatible. At least two were after raising the test voltage to 12V, with a view to using something more potent than the design PP3. (A note on preceding page says PI-1 only should be OK to 12V)

Checking the specs of this chip, it's rated for 2-6V, so I'm thinking it copes with 9V, but gets dodgy by 12V. There must have been quite a few builds of this circuit over the past couple of years, so must be OK at 9V, I would think.

Ray

Thanks Ray. Yes, I can confirm you are correct. The pin numbers are screwed up on IC4. That's was one of the drawbacks of manually redrawing the schematics in Visio.

Your timing is perfect, as Carl and I are currently working on a second revision of ITMD. Our stock of books is almost exhausted. The new revision will mainly consist of updates and amendments (as per the Errata List). This time we'll be ultra-careful with the pin numbers and reference designators, etc. No doubt some eagle-eyed readers with spot further errors, but hopefully the number will be much smaller this time around. We're also in the very early stages of planning a more advanced version ... but that will take some time, so don't hold your breath.

[WM6]

Your timing is perfect, as Carl and I are currently working on a second revision of ITMD. Our stock of books is almost exhausted. The new revision will mainly consist of updates and amendments (as per the Errata List). This time we'll be ultra-careful with the pin numbers and reference designators, etc. No doubt some eagle-eyed readers with spot further errors, but hopefully the number will be much smaller this time around. We're also in the very early stages of planning a more advanced version ... but that will take some time, so don't hold your breath.

Qiaozhi & Carl - don't stop with your excellent work.

[bernte_one]

which you much succes
i am building all pi from the book step by step
for the proof of concept

hope for more bugfixes i will put it in my book

[bernte_one]

have woked out a sprint layoput version of pi-1, are then anymore changes in silkscreen layout than q3
q3 should be reversed as the errata list say

[Qiaozhi]

have woked out a sprint layoput version of pi-1, are then anymore changes in silkscreen layout than q3
q3 should be reversed as the errata list say

IC4a (74HC221) has 2 incorrect pin numbers. Pin 5 should be 13, and pin 12 should be 4.

[bernte_one]

IC4a (74HC221) has 2 incorrect pin numbers. Pin 5 should be 13, and pin 12 should be 4.

is this incorrect by the layout or in the schematic

finished soldering yesterday, and broke my brain by soldering the q3 2N3819 corrected
would be better to use a mpf102 and reverse it 180 degree

i can adjust a light humming sound without the coil connected, if i connect the coil the irf9630 get hot and i got no detection

so i thing i should check the ic4a 74HC221, at the monet i have used original layout like in the book but only q3 changed like in errata list

[bernte_one]

maybe this helps

[raygdunn]

Hi bernte_one,

I reported the problem in the schematic, whilst putting the PI-1 together on a breadboard. A couple of pin numbers were duplicated.

(My circuit has now been transferred to Veroboard and has clocked up 20 hours of use. I'm very pleased with the result. Despite my earlier suspicions of the CD74HC221E at 12V, it's been running happily for me as 11.7V, using a 1300mah LIPO. I was unable to get the background hum using 9V (PP3), but this appeared at the higher voltage. It otherwise worked at 9V, just not quite so sensitive. PP3 only lasted 3 hours, hence the battery upgrade. For me, PI-1 is much more sensitive than the PI-4, which I've just got running on a breadboard. The book does suggest this. )

Hope that helps.

Ray

[bernte_one]

ok i will try 8*1,2V for power supply on my pi-1, but i think i have still Problems with the irf9630 which gets hot in 10sec
or my 2n3819 is still wrong can i use also a mpf102 or is this totallywrong for that Project, 2n3819 is out of production and not a cheap part

[6666]

Make sure you get the pins correct.
http://electro-music.com/forum/phpbb-files/fet_978.jpg

[raygdunn]

Hi bernte_one,

More voltage sounds a bad idea at this point in time. Sorry I seem to have mislead you there. It sounds like most of the circuit must be OK, if you hear a tone.

If your IRF9630 is hot without the coil, then something is wrong somewhere, it is using only 14.3mA in my case. Below I've detailed my current usage and voltages, which I hope will give you clues. Whilst there will be no exact match, it does give you approximate voltages. I've included some figures without the coil attached, as plugging that in will increase the heat.

I have attached a small heat sink to my IRF9630, after making too many beginners mistakes (like short circuiting wires), it being my first significant project for 30 years. :-( My IRF9630 seems to have survived though.

I hope this helps.

Ray

PI-1 sample voltages etc.

8.9V bench supply With coil disconnected

Current 14.3mA

NE555P pins
1: 0.0
2: 4.2
3: 0.3
4: 8.9
5: 6.0
6: 4.2
7: 0.2
8: 8.9

IRF9630
S 8.6
G 0.4
D 8.9

2N3904
E 0.0
B 0.0
C 8.5

NE5532P
1: 6.9 (was originally something like 8V until I adjusted R6 from 6K8 to 10K I think)
2: 4.4
3: 4.4
4: 0.0
5: 4.4
6: 4.4
7: 4.4
8: 8.9

CD74HC221E
1: 0.3
2: 8.9
3: 8.9
4: 8.9
5: 0.0
6: 0.0
7: 8.9
8: 0.0
9: 0.1
10: 8.9
11: 8.9
12: 8.9
13: 0.1
14: 0.0
15: 8.9
16: 8.9

TL072ACP
1: 2.2
2: 4.4
3: 4.4
4: 0.0
5: 4.2
6: 4.4
7: 5.4
8: 8.9

2N3906
C 0.0
B 0.3 varies
E 8.9

2N3904
C 4.9
B 4.4
E 0.3 varies


8.9V bench supply with coil attached

Current 67mA

NE555P pins as above.

IRF9630
S 8.5
G 0.0
D 8.9

2N3904 as above

NE5532P
1: 7.3 (was originally something like 8V until I adjusted R6 from 6K8 to 10K I think)
2: 4.4
3: 4.4
4: 0
5: 4.4
6: 4.4
7: 4.4
8: 8.9

CD74HC221E
1: 0.3
2: 8.9
3: 8.9
4: 8.8
5: 0.0
6: 0.0
7: 8.9
8: 0.0
9: 0.1
10: 8.9
11: 8.9
12: 8.9
13: 0.1
14: 0.0
15: 8.9
16: 8.9

TL072ACP
1: 3.4
2: 3.4
3: 4.4
4: 0.0
5: 4.2
6: 4.2
7: 5.4
8: 8.9

2N3906
C 0
B 0.4 varies
E 8.9

2N3904
C 4.9
B 4.4
E 0.3 varies

My Circuit oddities, which will affect some voltages
The mid point voltage takes 10-15 seconds to settle and little or no sound until this completes.
I use a 10" coil made from 16 turns of some ancient 12V thick insulation multi-strand wire, so R2 damping resistor increased and pulse width decreased by reducing R21 to 7.5K (initially used 130mA and now 67mA)
I adjusted the pre-amp output voltage down from around 8V to 6.9V. I'm now not sure this was needed.
No speaker. Headset wired in serial giving about 68 ohms. Volume reduced by increasing R19 from 10 to 22 ohms to reduce volume.
With the unit out of its case, the audio is near zero, so may affect my audio stage collector voltages.

[bernte_one]

thanks raydgunn
very kind of you

i grabbed a cmos which can handle max 6v, is this ok? i read you have them too
http://www.reichelt.de/74HC-221/3/index.html?&ACTION=3&LA=446&ARTICLE=3170&artnr=74H C+221&SEARCH=74hc221


you have also done some little mods, but i expected the design should work how it is

[raygdunn]

Hi bernte_one,

Yes the CMOS is required, not TTL, so yours is fine I've just confirmed that in the PI-1 instructions for the PI_1 build instructions.

6V limit? Well try it and see seems to be the case. 11.7V seems to work fine for the one I'm using, but maybe not 12V. It's doing very well to cope I've found its good to buy two or more of everything. I got though three 555s, before I realised that I had my terminals the wrong way round! Luckily they came as a tube of ten..

Ray