it snowed last night it's September and it snowed so I'm gonna hide out here in
my shop with a nice warm a cup of drink and a nice hot soldering iron and I'm
going to build a kit course the question is which one so I think I'm going to go
blindfold mode and into the bin and pull out this one what is this one
well let's find out okay what we got here he's got one I see in a pot and
handful of other bits and bobs well we can get a knob okay
don't need that anymore so what does this board say yeah duty psycho and
distortion may be the course and a fine adjustment and oh right I remember now
that kind of gives it away this is a test pattern generator it can do square
waves and triangle waves and sine waves meet so that chip must be a function
generator or a signal generator easier to read if it was right-side up focus
you know very good in the assortment of parts down here you know a terminal
block we have the ten turn potentiometer 502 5505 pillar or five K ohms I think
our is it 1:21
to check that got any single turn trimmer pot thank god it's the normal
potentiometer what that knob goes on so that will be I assume the frequency
adjustment the course frequency adjustment and then yeah okay and then
that tin turn part will be a 5k there it is there and these other two pots like
that ones at 20k and that one's 100k are they marked no but I can measure them
alright huh that's this clamped up and start soldering the only thing I'm
disappointed in so far is that there's no socket for mr. chip maybe you know
dig into my what is this 2 4 6 7 14 kinship let me see what I got in stock
lame I'm not offended by soldering directly onto it but why risk damaging
it with my crappy soldering let us quickly take the time to grab the
datasheet for this thing it is an IC L 803 8 which is a precision waveform
generator voltage controlled oscillator
and apparently from inner cell or the original manufacturer is it our Reni
sass I guess it is no longer manufactured by them this one that I've
gotten may or may not be one of theirs it might be an aftermarket doesn't
matter what does it have to say for itself the frequency can be selected
from point zero zero one Hertz to up to 300 K which is more than enough for most
of the things that I'm doing features low frequency drift low distortion high
linearity wide frequency range variable duty cycle that's good and it can drive
up to 28 volts output Wow so the chip itself p1 is a sine wave
adjustment pin to is sine revote pin three is a triangle wave out duty cycle
and frequency adjustment on 4 + 5 v + input frequency modulation bias to know
connects sine wave adjustment V - or ground timing FM sweep input and a
square wave output that's kind of neat and internally there it is supply
voltage maximum 36 volts output current sync twenty five milliamps supply
voltage minimum single supply is 10 volts maximum 30 volts can you'll have
to remember that I'll probably run it on 12 ish or so and there's what's going on
inside it oh it's if you want to build your own
the hard way some design tips on reducing distortion and how to select
the various resistors what I'm not going to concern myself with that because we
have already got that figured out by the kit manufacturer if it doesn't work I'll
come back in here and do it the hard way but for now let's just trust that
they're not completely useless alright so we know a little bit more about that
chip I do have some 14 pin dip sockets which I think I will put one on you for
a mechanically fit right so let's decide what to put on first thinking oh I see
it diode in here what is he doing I didn't notice a diode on the on the
datasheet that diode is a reverse protection diode nicely done get makers
you can't screw up and put the put the power in the wrong way okay we'll get
that in there I'm doing you no particular order okay so we have a
capacitor there c104 a little sorry what is that c1 it so a 104 c2 and c3 okay so
there's two 104 caps of the Oh little ceramic variety that's those two guys
I'm gonna poke in a bunch of components just so I don't still keep flipping back
and forth you could do it in a different way if you wanted to but I'm not too
concerned if you wanted to say build part of the circuit and then tinker with
it and build part more and change it I don't think I'm gonna do that this is
just if fun a little weekend kit build so there's a few components in grab my
advice I don't have many places this is one of them one thing I like about this
it's got the grooves in the jaws it that's really for grabbing onto round
stock but it works really well for grabbing on to a board and holding it I
don't have one of those fancy little board holder things like I've seen some
guys on YouTube use I do have one on order but it's not here yet so I'm not
too concerned about it okay so let's just get started I guess
this is the diode and I'm using this little lamb I mean this little chisel
tip it's not the finest tip that I have for my iron but it's a little bit bigger
for through-hole work and if I was doing surface mount I would probably put this
tip back on but for through-hole work this one's just fine
I was actually doing some desoldering a little while ago on something that's why
I put the bigger tip on and I just stuck with it because it's not that big a deal
this certainly is gonna take enough board for it to matter okay it's those
two guys and that's this other capacitor over here there we go
grappling cutters
there's those guys nothing shorted okay what should we put on next
Jeevan led that's marked as d2 on there there's the flat spot that side can't so
I'm going to guess that that goes yeah probably have a resistor in series with
it okay so I'll put the LED and I'm gonna
put the other two ceramic caps in there one of them is booked at 102 and ones a
103 there's the world 3 there's the 102 so which one is this and my fingers no
that's the 103 just c4 yeah I like these and I'd like to see the schematic of it
but this is gonna be pretty close to what we saw on the datasheet and the
board's got the silkscreen with all the values on it and everything so I'm not
too stressed again if things go horribly wrong we can always troubleshoot so the
two little ceramic capacitors which are in parallel with each other so what are
you guys doing smoothing and decoupling
probably well they're not exactly in parallel well they're not at all they go
- that's ship that's one of the parts okay between one of the pots and a bus
that's better get better heat transfer and keep the angering nice and clean and
then this led so that's that's one of the power inputs up there these two had
power inputs I think no wait let's just see what's going on here so that's the
ground and that's the sunny so the ground is this trace here which those
two caps go to ground this little cap here that we saw it an arrow goes to
ground one side of the LED goes to ground and then it connects up to the V
- and then the V pus is there and that's the diode okay
so here is the led
wow that's really standing off that's okay I'm not doing this for beauty
points I just want to have a functional thing
and this guy won't look at PWM generator that I pulled out of my mailbag a week
or so ago we'll just add to my supply of test things okay what are their
capacitors do we have there's an electrolytic there it is that says 100
micro farad that's his 220 micro farad's
remember I said I trust these guys well
okay so the negative voltage Ian in the ground are in parallel and this
capacitor just across the negative on positive all the trucking so that is
just power supply smoothing so it doesn't matter that it's a it's a larger
capacitor then what the board silkscreen says it'll actually do a better job or
at least better at taking out large fluctuations anyway so what next
find some resistors so there is a zoom in here so we have one 10k there 110 key
there 110 key to go 310 case that's 200 old them 1 2 3 4
33 Ches all right
310 Ches okay that's those guys 1 200 oh and 433 k ok so that's those guys and I
think I've mentioned this many times before that I am somewhat colorblind but
I'm going to I'm pretty confident that those are the 33 caves up there and
there's three of those guys will be the ten keys there's my 200 ohms I was
fairly confident than that
so my 10k just gonna stuff these guys all in I think I'll start up at the top
here just just cuz I am going to bend the lead over in the direction that the
trace goes away from the pad just to keep it kind of orderly so it doesn't
cause problems later potentially it's not a big deal it's just
hmm see if I get a little bit big um blobby like that it's not overhanging
adjacent trace now it's just on top of its own trace so that's not a big
problem now we keep the tip clean
I'm not even doing this yeah that's starting to get a little bit you know
forest in there so I'll just clean some of these out of the way let's see what
I'm doing that's the one disadvantage of stuffing a bunch of components in
simultaneously so it kind of gets in your way a little bit later on but it's
not a big deal he said that one since they both want to bend the same
direction I'm just going to do one first and then I'll hold it now they're the
other one and the last one this guy's just hanging off the end of that chip
socket try not to get too obsessive amount of solder in here but you can
also go to light which isn't gonna help anybody out either okay that's all the
capacitors and fixed resistors and diodes next let's put in well let's put
in the chip I mean the socket so the divot goes that way these sockets also
have a divot on them now this one going to have to use the you tube solder errs
favorite technique blue tack or blue sticky generic stuff yes of course this
isn't branded boo tack this is from the dollar store
let's pick up the four corners to hold it in place and then there's quickly
baying these off
walking again okay where's the socket on the boot Tech didn't get goopy that's
good right let's put in the ten turn pot and it doesn't really matter which way
up it goes but there's a little one section two sections so I'll put it that
way with the screw at that end it really doesn't matter because the white period
comes down the middle anyway
okay those guys a little bit uh what else swords a big pot which is also a 5k
according to silkscreen on the board goes in there
and I think I'm going to nudge those little mechanical grippers in i'll
solder them first they're gonna take a lot of heat let that's I'm just pushing
on the back of it to reflow that so that it goes into place well for those ones
they're not an electrical connection there's the mechanical connection you
don't have to fill the hole and I decided not to but they are making a
mechanical connection now so they're doing their job there's the little
switch which is frequency range low and high I'm guessing and it's just a
single-pole double-throw switch and again it's got two little mechanical
weeds on the end of it
a 104 and a 203 okay 104 is one a zero and four more zeros so that would be 100
K which also says 104 right on it and the other on 203 20 K yep
that is the duty or duty cycle for the square waves I'm guessing because sine
waves don't really have a duty cycle
so boat all that's left only one thing left to solder actually and that is the
connection pins but again oh it's wrong punch it in there so this one actually
the two ends the negative voltage in the ground
which are the same that that whole trace it wraps around there they also have
three little tags of solder or of a copper they glow it onto the ground
plane so that's that's nice that just keeps noise down by having that ground
point everywhere not that it's a big hairy deal in this
thing because it's gonna kilohertz range literally hundreds of kilohertz but
still if it was going up into the very high kilohertz and into the megahertz
into RF range and a ground plane would be a very good idea did I get those off
yeah it looks like they're all making connection just one more inspection here
everything's got solder I don't see any solder bridges right that chimp pins are
a little bit caddywhompus or not too bad but you know did of an alignment there
not too bad that way okay the notches on that end dot four pin one notches on
that end so I'm just but one row of pins in and it's to push the chip against
that to get the second row in make sure they're all nothing's hanging off the
edges and just push it down nice and evenly
joke there it is all right no to test okay a little bit time is past I got my
test setup set up here like 12 volts on the power supply oh forgot about this
guy critically important get the knob on there right yeah I think so that's the
frequency knob according to the information on the board anyway um so
I've got el cheapo scope set up here on little kickstand and I just recently put
together hallways paused power supply connected to positive a negative at the
ground of the scope connected to the ground so when you turn the power supply
on and got a power LED that's an excellent start okay so these two pots
set on all the pots pretty much set to the middle this one I've got this
fine-tuning that set about the middle of its range and I mean the high range here
for frequency so oh let's go on to the square wave oh come on
automatic stuff um there we go that should be a lot easier for you guys to
see - I've made some changes my camera it's an auto exposure so when i zoom
back out from the black background of that it's gonna get a little weird but
whatever at least you can see this now so right now our square wave 50 ish
percent duty cycle which makes sense because at that pot set in the middle
voltage peak to peak is 11 volts that's pretty close to rail-to-rail since I'm
running 12 volts what else so I'm at two point three seven something kill Urtz
and that's with the pot set in the middle position I'm gonna crank that up
to maximum and scope now that is two point eight four
six I'm just going to go in and tweak the finetuner up should be about five
turns I'm hoping if it's ten turn puck
what's that six point one five one okay now I'm gonna flip the high or low range
switch to low five hundred and ninety six and I'll crank the pot down as low
as it'll go and then off scale so let me just change the scale and the scope here
what's wrong way change of time based on the scope I guess there you go fifty
Hertz oh look at that non-linearity down there that's disturbing I wonder if the
distortion part does anything about that you know I'm thinking the distortion
part has to do with sine waves okay well that's not super awesome we're going to
a 50 Hertz Oh what so let's change don't you know I'm gonna crank that back up so
you can see the hood hmm okay where were we before my kickstand fell over so
right now yeah I'm gonna start tweaking the duty cycle pot right now it's kind
of in the middle go down to the bottom 67% go to the top 23% okay but I hadn't
really expected this thing to be a PWM generator anyway that's what this thing
is for which is exactly a square wave frequency and duty cycle so I'm not too
stressed by that so that's all right for square waves where is it
yeah real let's move on to triangle and sine waves I'm going to just bump that
sensitivity up a little bit so there's the triangle wave and again I
will tweak the various parts and locks but the duty Seiko
oh yeah it goes from just a straight up-and-down triangle wave to more of a
sawtooth wave that's interesting with the debts with the duty cycle part let's
try the distortion part that doesn't really do anything and of course the
frequency so that's the top of the low range which is was at 570 and again down
to 50 ish which is pretty much there you oh that's curious there's that
distortion part you see that zero crossing yeah that's interesting
does the distortion pot do anything about that
not really so a triangle waves not SuperDuper linear that's the duty cycle
up in the kilohertz that's not super duper leaning it's got a little kick in
it that's disappointing let's go back down into the middle of the range so
that is coming out of there and what is it it is out of focus sorry so that's
coming out of there at three volts peak-to-peak or as a square wave was 11
volts peak-to-peak okay now a sine wave so I leave is 2.3 volts peak-to-peak
it's a little bit distorted too in the middle now this has changed the
distortion part well that's disappointing let's go back down to the
low range and get changed a tiny base of the scope again so there is something
it's not it's not a perfect sine wave hmm I wonder how it sounds I was hoping
to use this for testing audio amplifiers and I was hoping to get
relatively clean sign leave out of it this isn't that
yeah that's not performance that's that maybe inaudible this is a 4 kilohertz
that's not going to be a huge thing but it's still not what I was hoping for
Oh duty cycle does affect the sine wave too I mean the zoom mode so we can see a
couple of sine waves so there's the duty cycle roughly in the middle okay so it
doesn't lean it around a little bit that's pretty much a little okay well
it's not not the best most accurate most precise thing in the world but I think
it is a little bit cleaner waveforms then this guy was giving me but I so
I've got to signal sources now this one you may recall it's a 555 timer and then
it just uses these RC filters to knock out the high frequency components out of
the square wave to create sawtooth and then a triangle wave and then event or a
sine wave and as it goes through those passive filters the amplitude just gets
a lower and lower through each stage this one at least it's relatively
consistent on the triangle and the sine wave four levels the square wave of
course is it's still hitting rail-to-rail
but I don't know it was a fun we'll get to build anyway thanks for watching
preciate you stopping by questions and comments as always down in the comment
section yeah thanks for stopping by I'll talk to you later
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