Electrical Engineering

8:09 AM

@tyblu tits?

10:12 AM

@jim

yellow :)

How would you like a nice 440Hz sine wave?

@MattJenkins sounds great!

@MattJenkins Is this an audio out thing?

Only 8-bit resolution, generated by a dsPIC putputting on 8 IO pins to an R-2R ladder. The frequency is controlled by an ADC input (pot) and I can get anything between 104Hz and 2.2KHz

@MattJenkins did you say you might be getting some dsPIC33FJ128GP802s ??

@MattJenkins very nice

10:16 AM

Yeah - they are in the post from thailand or somewhere

@MattJenkins will you be waiting long?

Normally takes a week or so - been getting on for that so should be here soon-ish

@MattJenkins cool - was going just post you one out but it'll probably take just as long

my deep cycle battery is now on its second day of trickle charging - it was holding 8.7v last night, here's hoping it'll reach 12v today

@MattJenkins Wow - nice trace!

10:21 AM

You can't see the jaggies very much there, but IRL it's quite a pixellated waveform.

@Jim cool

@jim Do you use dropbox?

@MattJenkins according to Olin you can use smooth interpolation on the dsPICs to remedy that

@MattJenkins very much so

I'll email you a link

@Jim Not when you only have 8 bits of output resolution - it can't magic more bits than you have...

I do all my work inside the Dropbox folder - makes it so much easier to switch from laptop to netbook to desktop to phone ;)

@MattJenkins humm - I wonder what he was on about

He was on about interpolating between samples to change the frequency

reduce the harmonics created by changing the playback speed of a wavetable

brb

10:29 AM

Randomly generated wave-table. 360 samples of randomness.

@MattJenkins noise - nice

More of a farting sound.

Shall I send you a share request for a folder?

Or do you want to send one to me?

@MattJenkins I'll set one up, I've got plenty of space

give me a mo

The space is irrelevant - he who creates the files owns the space used.

@Jim At higher frequencies it looks like one of those magic-eye pictures.

@MattJenkins I think I've sent you a Dropbox

10:39 AM

I have got a dropbox

I have dropped in the drop box

@MattJenkins I've got a file that says "Hello" :)

Heh

2 Sines added.

@MattJenkins very cool!

it looks so smooth

that's the camera's fault ;)

@MattJenkins what scope is that?

10:52 AM

A "Feedback" OS-9020A (re-badged goldstar)

@MattJenkins ah - I did real 'Feedback' and I thought 'I wonder what the hell that is' didn't realise that was the manufacturers name

heh

can we do bold ?

yes

And bold italic

test

test

weird

11:07 AM

*******

bbiab - garden center calls

:)

11:35 AM

I think I have the baud rate figured (still no joy with the LCD tho)

// internal osc = 7.3728 MHz
// internal osc ÷ PLL pre scaler × PLL post multiplier ÷ PLL post scaler ÷ 2 (number of clock cycles per instruction)

...and I have a pre scaler of 2 a multiplier of 43 and a post scaler of 2

so that gives me 7.3728 ÷ 2 × 43 ÷ 2 ÷ 2 = 39.6288 MIPS

...so 39628800 ÷ baud rate (9600) ÷ 16 - 1 = baud rate pre scaler

...and that gives me a grand total = 257

I'm pretty sure about that baud rate pre scaler, not quite sure why it's divided by 16 and minus 1, but it is outlined specifically in the dsPIC33F UART Family Reference Manual

so I'll trust it for now

I think I must have goosed the settings on the LCD by sending it random commands while trying to set up the UART coms - oops

12:15 PM

hello folks

hey @Kellenjb :)

@Kellenjb you good?

im great

just waiting for @kortuk to wake up

@Kellenjb He's a busy guy, you can't begrudge him a little rest ;)

@Jim but i am offering him food, so he should be happy

@Kellenjb well there's no excuse for that - go poke him with a stick!

das code ->

#include <p33Fxxxx.h> // header file for my specific PIC chip

_FWDT(FWDTEN_OFF) // set watchdog timer off
_FOSCSEL(FNOSC_FRCPLL) // fast RC oscillator (internal) with PLL

char fade_dir = 1;

void delay(long i) // delay for a given number of cycles
{
while(i--);
}

///////////////////
// main function //
///////////////////

int main(void)
{
RCONbits.SWDTEN = 0; // disable watchdog timer

///////////////////////////////
// set system to 39.6288 MIPS//
///////////////////////////////

hummm- rain, better get that battery and charger inside quick!

12:27 PM

@Jim we finally got rain last night! it was amazing

we are still expected to be in a drought until end of October though

@Kellenjb dude, not cool - we have loads of rain and storms right now, you can have some of ours

send them our way!

@Kellenjb I'll start blowing now

I'm all out of breath tho, just got my exercise for the day, lifting that damned heavy 110 Ah 12v battery inside- just about broke my back!

I should check to see what it's holding now- fingers crossed :)

@Jim at my old job we powered everything with marine grade 12v batteries. they were a pain to move around

hummm 8.3v - well at least it's getting better and it hasn't dropped

for some reason my multimeter will only measure dc voltages in reverse polarity - I think it's about time i got a new one

12:38 PM

@Jim sounds like a diode or a fuse isnt happy

@Kellenjb probably -it's been like that for months now, I should open it up for a look, it's not like it was expensive

got it from a market for £5

surprised it's lasted as long as it has

wow - there's only one microchip inside this multimeter

it's just a cheapo blob IC, there's barely anything on here

there is a fuse, lets see if i can use the continuity tester on the meter to test itself :)

12:54 PM

@Jim That baud rate pre-scaler works perfectly with my PC - it must be the LCD

@MattJenkins cool - cheers for trying it, I'm not sure what's up with the LCD, It looks fully functional but the settings could be all messed up

probably

Trying to fathom how to get 2 ADC values from this thing now

Q: How does earthing work when earth is dry?

1:12 PM

Is there some place in there world where there is 0 water content in dirt for all 20 feet down?

1

Earthing is meant to provide reliable contact of an electric appliance to earth so that if there's an insulation fault current goes into earth instead of through a person's body. This requires earthing to be made of thick conductors driven deep into earth. Here's how good earthing was described ...

I think i'm destined to not get any real time feedback from this chip, this LCD is just crazy, it's been in a box for quite a while- maybe the code on the EEPROM is knackered

@Kellenjb maybe death valley?

there can't be that many places- humans rarely live that far from water

yeah.

I guess it only has to earth stuff better than the next best earthed object

@Jim You need my MAXDB9 breadcrumb, then you could interface it to your PC with no hastle...

@MattJenkins is that the serial coms board you made?

1:17 PM

yah

maybe I could use an arduino

If I sent a value using the UART on the PIC, do you think I could capture that via the serial Rx on an Arduino?

Should be able to, yes.

wondering if i am capable of making a PCB antenna

@Kellenjb you can always make an arbitrarily sized one and use a tuning cap?

@Jim i can? :-D

1:29 PM

@Kellenjb if you make the antenna roughly the right size you should be able to adjust the resonant freq with a tuning cap

question I have always had is how do i know when i have it turned, and how do i know what the tuning network needs to be (with out proper equipment)

@Kellenjb it's how I tune the transmission freq of my FM transmitters

i think there is a question on here, but i seem to remember it not having any good answer

@Kellenjb depends on the freq, but a radio can help

3

Q: DIY Antenna Tuning

I know that getting a perfect tuning network for an antenna and transceiver requires some rather expensive equipment plus human knowledge to operate the equipment. I have never done any antenna tuning, but I would like to know if there is any way a DIYer can perform at least a semi-decently good ...

antenna

one of my questions :-)

1:34 PM

@Kellenjb cool - I'm not sure what would help, I'm just a novice - but you can tune a radio to your required transmission freq then just adjust your transmitters freq until you audibly hear it block the static on the radio

use a plastic tipped screw driver or a well isolated tuning knob or it'll be real hard to get it spot on

this all depends on what freq you want and the bandwidth of your radio

if you already have the receiver module - maybe you could hack on a speaker so you can snoop what's going on

i have been thinking 915 or 433

MHz

I'd stay away from 433

why?

It's been / being opened up to voice - it's gonna get kind of noisy in that area.

I'd use 868 or 915

oh, hmm

my previous job used 433 for almost everything

1:41 PM

433 is being used less and less for digital. There's also some kind of terrestrial network thingie that's been licensed for that range too can't remenber what it is off hand - could casue some problems.

433 for all of the clients and then 915 for all of the back hauls

although, the device is for cows, so generally there isn't much other wireless activity going out out there

You have digital cows? The iCow?

we took their temperatures and would tell you when they were sick and then could tell you who they hung out with

@Kellenjb that's so cool

@Kellenjb I wonder what a game of 4 square would look like if it was played by cows

@Kellenjb Anti-TB technology?

1:45 PM

it is capable of alerting that the cow is sick a few days before a vet would be able to tell, and then the location tracking was to be able to stop the spread of an outbreak without having to stop commerce

Nice

@MattJenkins the general disease that we use as a reference was foot-and-mouth

Just as valuable ;)

Hmmm... I have broken ADC completely now :(

it would be awesome if it ever made it to market

2:14 PM

@MattJenkins how come?

did you cook it?

No, I just messed up the sample clock

@MattJenkins Ah right, I'm sure you'll get it sorted

right now I have the PICfred hooked up to the Arduino's Tx

it seems to be working

Cool

I have 2 analog inputs now - and each one is tied to a different frequency wave, then I add the two waves together...

@MattJenkins nice - modulation!

I can get chords ;)

2:19 PM

I'm just trying the printf with the arduino serial coms

@MattJenkins very cool!

I had mixed results with printf

Just printing a string was fine - as soon as I tried to use any form of formatting it just broke completely

ooh - it's working

It's printing bla whoop yeah in the arduino serial monitor now :)

nice

there's no code on the arduino except for ->

void setup()
{
Serial.begin(9600);
}

void loop()
{

}

and I've just hooked straight up to the Tx pin :)

lol

2:22 PM

I wish I could set the PIC baud with Serial.begin(9600);

it would be much easier

It would be nice, but then, would you understand how it actually works?

(do you now? ;))

@MattJenkins Mostly I just need it to work - I only want to know the nitty gritty when it goes wrong ;)

@MattJenkins that's smooth!

great work

@MattJenkins you know how to get printf to print on a new line?

\r\n

cheers

This is all interrupt driven, too, so the main loop is just:

while(1);

2:29 PM

doh - that doesn't work :)

\r\n is for the pic i'm printing to the arduino console oops

now blaa whoop yeah looks crazy!

\r should return to the beginning of the line. \n should move the cursor down one line

same number of chars just loads of weird symbols :)

@MattJenkins but that's on a PIC

I'm sending the commands thru the Arduino

That's the standard for serial communications

okay

character 13 and character 10 (CR,LF)

2:35 PM

ah - got it now

think I'm having sync problems

Do serial coms have to be synchronised, or can I just spew data at the arduino as long as it's at the right baud?

You can't send data more rapidly than the receiver can handle. It depends on how big the receiver's buffer is.

heya everyone

Lo @Rick2047

@Rick2047 hey :)

quick question, what is the best type of paper for toner transfer method?

2:47 PM

@MattJenkins so I'm probably messing up the buffer, humm, will have to have a think about this

You want it shiny but not photo glossy

@Rick_2047 I know this

give me a second, I've done much experimenting with this

@Jim ks

@Jim also tell me if its necessary to clean my copper clad board with benzene before I start

@Rick_2047 I've got a video on my channel done by my partner, the method is tried and tested over a thousand times

@Jim link

2:51 PM

►

that's the video

here's the comment -> Buy cheap gloss paper for colour laser printers to get the best results, own brand Walmart in USA or Staples in Europe works good for us

@Rick2047 ignore the staining part :)

@Jim what about the alcohol is it really necessary?

@Rick_2047 yeah - you need to use something to get the surface clean and grease free

@Rick_2047 you can use acetone tho

@Jim what are some more easily available options?

@Rick_2047 the alcohol is just rubbing alcohol it's cheap and easy to find - but If you don't want to use it then acetone is the next best thing

you'll have to remove the toner afterwards and believe me it's tough to shift!

now where will I get some acetone

2:57 PM

I have had quite good results cleaning the board in warm water with washing up liquid in it and a small wad of steel wool

this is the paper I normally use

@Rick_2047 acetone is just nail polish remover

or you can get pure stuff from a hardware store

@Jim oo, off to raid my sisters vanity case

they sometimes put moisturiser in the nail polish remover - not sure if that'll be a massive problem tho

@MattJenkins is right some steel wool would work - but you will have to be careful not to remove the tracks

I use my fingers to rub off the paper - the steel wool is only for the initial cleaning and the final toner removal

@Rick2047 if you look at the end of this video you can see the kind of quality we can get using this method -

►

@MattJenkins for sure - you want to be really careful removing the paper - patience is key, let it soak!

3:01 PM

Yup

I use a dish scrubber to scuff the back of the paper so the water soaks in easier

The paper I use is some old posters from a charity. A4, and 'magazine' type glossy

I am not going to print it myself

its going to be printed by my local photocopier in a standard zerox machine

should that be a problem?

@Rick_2047 It has to be a laser printer otherwise it will not resist the acid etchant

laser or inkjet?

3:06 PM

@Rick2047 and you want to be careful to protect the print from dirt and finger grease after printing - you'll need to protect it while you take it home

@Rick_2047 it must be laser

@Rick2047 make sure you handle the print with super clean hands as any touching of the toner will stop it from transferring well

@Jim now you are scaring me

but they handle glossy prints well

@Rick_2047 It can take some practice to get the best results - but I guess it depends on what scale you are printing on

i am just making a usbasp for a friend

@Rick_2047 maybe it will take you a couple of tries to get the toner to transfer well, you can always scrub it off and try again - make sure you get 2-3 prints so you have a backup

yeah I was planning to do that, the circuit fits in 1/4 the A4 page so I can get 4 prints

3:12 PM

@Rick_2047 that's a good idea

@Rick2047 it's the type of thing that can take a bit of practice to get super sharp results, but once you know the process it's very repeatable

@Rick2047 did you see the boards at the end of the second video?

@Jim yes

@Rick_2047 I like the decorated one - I have it on the back of my PC monitor :)

Hey @KevinVermeer :)

the one in the last row?

@Jim Hey! Just trying to debug some chat problems. Do any of you run NoScript?

@KevinVermeer i've got it on my other computer, want me to check something?

3:17 PM

@KevinVermeer no script? what like no javascript

@Jim yes, its a firefox pluging that lets you control where scripting is run

Q: "Please log in to any StackExchange site first"

@Kellenjb What is on your whitelist such that it works for Chat?

I'm trying to work on this question:

0

When I want to go to chat I get this message at the top of the screen, while I'm logged on on at least 5 Firefox tabs! If I remove the message and click on login the message comes back. So I can't chat. Firefox 3.6.18 on Windows XP w/ SP3.

support chat

nah - I'm just on google chrome

@KevinVermeer i've never used SE chat in firefox :-)

i'm on chrome these days, let me go play with it a bit though

@Kellenjb Sure. From a brief look at the source, I'm guessing that or.sstatic.net (the StackOverflow CDN) needs to be whitelisted.

But that would make a lot of stuff fail to work.

3:21 PM

@Rick_2047 sorry dude - yeah the one in the last row, the thin parts are really sharp, my girlfriend made it for me, it's a really nice piece

@Jim cool

@KevinVermeer chat works for me without specifically allowing anything. looks like sstatic.net is in my whitelist though

@Kellenjb Hmmm.....

@KevinVermeer do you have googleapis.com in your whitelist?

brb

3:25 PM

@KevinVermeer also have you tried chat.stackexchange.com/help

@Kellenjb I'm not running NoScript at the moment, @stevenvh is. I think it should work with googleapis.com blocked, the problem is with the auto-login popup (which is SO code and not on googleapis.com).

@Kellenjb Yup, that was suggested by balpha.

b

Thanks for your contributions!

Hey - Who changed the tagline? I guess I can let y'all moderate yourselves here. Enjoy chatting about beer and underwear; I'm off to lunch.

@KevinVermeer we're changing it again to cider and knickerbockers :)

enjoy luncheon!

beer and underwear <- was that @Kortuk ?

It's all a ruse anyway, we're all secretly talking about PCBs and electronics :)

3:42 PM

@KevinVermeer i tend to trust people. i pretty much allow all scripting except for ones that i know i dont want

hey @Kortuk how are you?

Kortuk

@Jim Im back

Day off and an inbox of 11

@Kortuk 11 that's not too bad

Kortuk

><

doesn't seem to be any serial communication happening now, I changed the PIC prog to only send something when the light was fading down- strange

when I was bombarding the Arduino stuff was getting through - momentarily

humm - sometimes I get data, sometimes I don't, it must be a buffer or sync issue

hey @Dean :)

Dean

3:50 PM

hello