field test unit no 001 "model T"

[hdphilip]

rotary encoder

Rotary encoder problem solved!

(forgot the pull up resistors)

Philip

[hdphilip]

6666,

I used the negative photo resist,

MG chemicial 416 DFR

i make the transparency on my laser printer

making pcb's pretty easy, it just takes a few tries to get the exposure
right, i find 6 minutes with a "black light" at 12 inches works,

here's the board before i etched it.

the two boards on the side of it are for input blocking fet ideas

Philip

[6666]

Good job Philip
what method did you use to make the PCB ?

[hdphilip]

rev 003 front end pcb

so far so good on the front end pcb project, can't wait til i start testing it!

I decided to make the "series blocking fet on it's own plug in board for testing, right now i'm going to just stert with the diodes first, then I can just change board to see what the performance differences are.

the trimpot (next to the voltage regulator) is inserted between the gnd and the 7805 gnd tab, set to about 5.3 volts

for some reason, i'm still having a few issues with the rotory encoder,

Philip

[Midas]

hello midas,

lol, i was thinking that, i have a old computer with that, also i was thinking about doing it
in circuit, because of the power requirements.

Which front end have you had good luck experimenting with?

Philip

Hi Phil,

Yeah I have a second machine pretty much exclusively for that purpose that I hook into using a program called tightVNC. Its good, saves having to keep swapping monitors\keyboards and mices all the time. I've not managed to build either of them... too much procrastination.

Midas

[hdphilip]

hello midas,

lol, i was thinking that, i have a old computer with that, also i was thinking about doing it
in circuit, because of the power requirements.

Which front end have you had good luck experimenting with?

Philip

[Midas]

moodz,

I'm going to build the 4012 first, then experiment with the different front ends, I'm making the PCB now. I do have the 4011 chip also.

I found some software, "PICPgm development programmer 1.6.4.2" that I'll try to use to program the dsPIC30f4012 with the jdm programmer.

Philip

You'll need the increasingly rare, 'real' serial port. Most if not all USB or PCI adapator serial ports don't work with JDM style programmers. Manufacturers of these devices have very little respect for the RS232 standard... 5v.. 12v.. what's the difference..

[hdphilip]

moodz,

I'm going to build the 4012 first, then experiment with the different front ends, I'm making the PCB now. I do have the 4011 chip also.

I found some software, "PICPgm development programmer 1.6.4.2" that I'll try to use to program the dsPIC30f4012 with the jdm programmer.

Philip

[moodz]

hello

I was thinking about building the UNIPI_DS_v320_R003 frontend, my question is..

where does the 'GROUND BALANCE IN' and the "DESCRIM BALANCE IN" connect to on the
cpu board, will this work with the 4012 cpu board?

looks like a fun project!!!!

Philip

Hi Philip ... the ground / descrim balance comes from one of the UNIPI PWM outputs ( see UNIPI chip ). This is a PWM signal and is adjusted from the LCD menu.

You should build up UNIPI chip / LCD controller board first then build the frontend. Note that these circuits are for experimentation mainly ...they are not a complete systemm yet.

moodz

[hdphilip]

hello

I was thinking about building the UNIPI_DS_v320_R003 frontend, my question is..

where does the 'GROUND BALANCE IN' and the "DESCRIM BALANCE IN" connect to on the
cpu board, will this work with the 4012 cpu board?

looks like a fun project!!!!

Philip

[moodz]

This new design is fantastic as a thought exercise how would its power be increased, in this design is the coil energized with 17V ?. Ignoring diminishing returns and battery weight etc is increasing the power as simple as increasing the voltage across the coil ?.

Basically yes ....I have a design running on the bench that gets more than 20 amps peak in the coil but draws around 70 ma from a 48 volt supply ( 4 x 12 volt lipo battery ). Resistance must be very low.

Moodz

[maca404]

This new design is fantastic as a thought exercise how would its power be increased, in this design is the coil energized with 17V ?. Ignoring diminishing returns and battery weight etc is increasing the power as simple as increasing the voltage across the coil ?.

[moodz]

Looking at the general block diagram of the THAT chip
do you think the lm324 amp would be ok for experimental purposes ?
with a pot for the gain

The only thing I am not sure of is the ref connection which is pin 5 on the THAT

the ref connection seems to equate to the positive input of the last lm324


Moodz has it going to positive, but the lm324 cct has it going to gnd
which should it be for our cct ?

Redrawn for your viewing pleasure. Note that the GBW of the LM324 is about 1 Mhz whereas the THAT1510 is is very much north of that. The LM324 could be used after a demodulator section. DC accuracy wont be stellar but it will work.

moodz.

[Aziz]

...just my two cents .... a differential amplifier amplifies the difference between two voltages ... ground does not come into it. The difference between the two voltages must only be less than the common mode range and gain of the amplifier. Because the output is single ended the ref connection is the "ground" ... however a true differential amplifier would have a differential output also ( not referenced to ground ).

( actually there is no such thing as ground .... electrons cant read ... they just move in response to magnetic and electric fields )

moodz

You forgot the gravity response force.

Guys, pay attention and don't loose any electrons while you swing the coil...

Shielding may catch them.
You know now, why there is a shielding.

Aziz

[moodz]

...just my two cents .... a differential amplifier amplifies the difference between two voltages ... ground does not come into it. The difference between the two voltages must only be less than the common mode range and gain of the amplifier. Because the output is single ended the ref connection is the "ground" ... however a true differential amplifier would have a differential output also ( not referenced to ground ).

( actually there is no such thing as ground .... electrons cant read ... they just move in response to magnetic and electric fields )

moodz