Need DDS module, 2nd round

[Spehro Pefhany]

You can keep a thermocouple to within a tenth degree of 25C by holding the lead
in your mouth, roughly 6" from the junction, sliding it a bit left or right to
keep the temp on target, varying the thermal conduction. You can even do it
hands-off with a bit of practice.

Pro tip: Remove thermocouple element from Inconel 600 thermowell
before attempting.

http://www.tantaline.com/files/billeder/Thermowell_Series385S.jpg



Best regards,
Spehro Pefhany

 

[Joerg]

Jamie wrote: [...]

I think you'll find if you don't have a latency problem with the
serial link to the chip, you should be able to do all the FMing you
want..

The problem with the uC on these little boards is not the serial link.
Well, at least not if 100Hz sweeps suffice. The problem is that they are
too small to calculate the numbers on the fly and usually have to little
flash left to store them in a LUT. Plus that would be a major
time-consuming hack.
Fancy ramped, modulated DDS sinewave generation at 200K samples/sec would be no
sweat for a $4 ARM, and you get a mux'd ADC and a DAC for free. But yes, it
would take some code slinging.

And I'll probably do that if this becomes a product, with whatever
processor the local SW folks can handle without a major learning curve.
Just not right now, got to watch work load, expenses and time line. So
it'll be analog for now.

If you do go ARM, let me know if you'd like some example C code to butcher. We
have an app that uses an ADC interrupt to do a filtering + PID algorithm, ADC in
to DAC out, on an LPC1754. The algorithm is pretty fancy, and we run it at 100
KHz with the internal uP clock throttled down to 50 MHz. We pay $3.55 each,
pre-programmed by a distributor.

Bring your programmer and we'll go to Zeitgeist and we'll explain our code and
the DDS theory. Your treat, of course.

That sounds good. Although this project would fit much nicer into a
Cypress PSoC because that has lots of useful analog functions in there.
Like S/C filters that can be pressed into service as mixers.

Today I'm writing a PowerBasic program to graph a bunch of thermocouple
temperature controller params vs time. It's slow, graphing coffee cups of hot
water cooling off. Thermal stuff is always tedious.

You can keep a thermocouple to within a tenth degree of 25C by holding the lead
in your mouth, roughly 6" from the junction, sliding it a bit left or right to
keep the temp on target, varying the thermal conduction. You can even do it
hands-off with a bit of practice.

I'd try to gauge the thermal effects of foam recombination on an Anchor
Steam OBA. Problem is, with me it won't stay in the glass for too long.

 

[[email protected]]

John Larkin wrote:
Jamie wrote:
[...]
 I think you'll find if you don't have a latency problem with the
serial link to the chip, you should be able to do all the FMing you
want..
The problem with the uC on these little boards is not the serial link.
Well, at least not if 100Hz sweeps suffice. The problem is that theyare
too small to calculate the numbers on the fly and usually have to little
flash left to store them in a LUT. Plus that would be a major
time-consuming hack.
Fancy ramped, modulated DDS sinewave generation at 200K samples/sec would be no
sweat for a $4 ARM, and you get a mux'd ADC and a DAC for free. But yes, it
would take some code slinging.
And I'll probably do that if this becomes a product, with whatever
processor the local SW folks can handle without a major learning curve..
Just not right now, got to watch work load, expenses and time line. So
it'll be analog for now.

If you do go ARM, let me know if you'd like some example C code to butcher. We
have an app that uses an ADC interrupt to do a filtering + PID algorithm, ADC in
to DAC out, on an LPC1754. The algorithm is pretty fancy, and we run itat 100
KHz with the internal uP clock throttled down to 50 MHz. We pay $3.55 each,
pre-programmed by a distributor.

Bring your programmer and we'll go to Zeitgeist and we'll explain our code and
the DDS theory. Your treat, of course.

That sounds good. Although this project would fit much nicer into a
Cypress PSoC because that has lots of useful analog functions in there.
Like S/C filters that can be pressed into service as mixers.

I just saw the new STM32F3xx, cortexM4 with all the usual interfaces
and up to four opamps/PGAs and seven comparators

-Lasse

 

[Bill Sloman]

I wonder what's the temperature of a well-stirred mixture of crushed ice,rum,
and Coke. That deserves further research.

A well-stirred ice bath, made with distilled water and pure ice, sits
at 0C (273.15K) to about +/-0.001K, if the US NBS is to be believed.
Adding anti-freeze is going to make it cooler and less predictable,
and there's a risk that your measurments will become less reliable as
the experiment progresses, not that anybody prepared to drink either
rum or Coke is to be trusted in the first place.

 

[Bill Sloman]

John Larkin wrote:
Jamie wrote:
[...]
 I think you'll find if you don't have a latency problem with the
serial link to the chip, you should be able to do all the FMing you
want..
The problem with the uC on these little boards is not the serial link.
Well, at least not if 100Hz sweeps suffice. The problem is that theyare
too small to calculate the numbers on the fly and usually have to little
flash left to store them in a LUT. Plus that would be a major
time-consuming hack.
Fancy ramped, modulated DDS sinewave generation at 200K samples/sec would be no
sweat for a $4 ARM, and you get a mux'd ADC and a DAC for free. But yes, it
would take some code slinging.
And I'll probably do that if this becomes a product, with whatever
processor the local SW folks can handle without a major learning curve..
Just not right now, got to watch work load, expenses and time line. So
it'll be analog for now.

If you do go ARM, let me know if you'd like some example C code to butcher. We
have an app that uses an ADC interrupt to do a filtering + PID algorithm, ADC in
to DAC out, on an LPC1754. The algorithm is pretty fancy, and we run itat 100
KHz with the internal uP clock throttled down to 50 MHz. We pay $3.55 each,
pre-programmed by a distributor.

Bring your programmer and we'll go to Zeitgeist and we'll explain our code and
the DDS theory. Your treat, of course.

That sounds good. Although this project would fit much nicer into a
Cypress PSoC because that has lots of useful analog functions in there.
Like S/C filters that can be pressed into service as mixers.

Today I'm writing a PowerBasic program to graph a bunch of thermocouple
temperature controller params vs time. It's slow, graphing coffee cups of hot
water cooling off. Thermal stuff is always tedious.

You can keep a thermocouple to within a tenth degree of 25C by holding the lead
in your mouth, roughly 6" from the junction, sliding it a bit left or right to
keep the temp on target, varying the thermal conduction. You can even do it
hands-off with a bit of practice.

I'd try to gauge the thermal effects of foam recombination on an Anchor
Steam OBA. Problem is, with me it won't stay in the glass for too long.

Beer foam collapses because the CO2 inside the bubbles diffuses out a
lot faster than O2 and N2 diffuse in - the latter two are much less
soluble in the water film than the CO2.

The thermodynamics might be interesting, but are probably too
dominated by the evaporation of water and ethanol justify any serious
measurement effort.

 

[rickman]

Thanks for the offer, that was nice. But meantime I already did it the
old analog way.

Too bad. Last night when I was reading some of your other posts in this
thread I realized you were looking for a module you could put on your
board. I have a module that would suit your needs with a little
programming of the FPGA. It has a small FPGA, a 24 bit stereo CODEC, op
amps and could do just what you seem to need. The programming would not
be a big deal. The job it was designed for is similar and mostly I
would just need to rearrange the code pieces a bit.

Tell me about it, I just designed a board full of 0402 parts and I'll
get to debug it later :-(

So, a few months ago I caved in and bought one of those Donegan Optical
head goggle thingies. Took the 5x version because some of my work is now
much finer pitch than 0402. I can keep my reading glasses on while
soldering that. I was at the point where I occasionally wore two reading
glasses stacked.

Yeah, I had a very nice one and someone walked off with it. I really
should break down and get another. They are worth their price. In the
mean time I have gone to using two pair of reading glasses. If I set
them on each other just right they give me three different
magnifications, tri-focals!

BTW, I dug into my sig gen this morning and I don't like what I found.
What I mean by that is I don't understand it. I'll post some details in
the thread I started about it a couple of weeks ago.

 

[Joerg]

Too bad. Last night when I was reading some of your other posts in this
thread I realized you were looking for a module you could put on your
board. I have a module that would suit your needs with a little
programming of the FPGA. It has a small FPGA, a 24 bit stereo CODEC, op
amps and could do just what you seem to need. The programming would not
be a big deal. The job it was designed for is similar and mostly I
would just need to rearrange the code pieces a bit.

Maybe next time. Nico had also offered to built one, which was nice.

Yeah, I had a very nice one and someone walked off with it. I really
should break down and get another. They are worth their price. In the
mean time I have gone to using two pair of reading glasses. If I set
them on each other just right they give me three different
magnifications, tri-focals!

http://www.mpja.com

Their site is currently not working properly but article numbers 17653TL
and 17654TL would be the head-worn magnifiers. Not very expensive. I'd
tell them not to ship UPS, they crushed the first one by tossing the
package over the backyard fence. The next one came via US mail, because
I insisted.

BTW, I dug into my sig gen this morning and I don't like what I found.
What I mean by that is I don't understand it. I'll post some details in
the thread I started about it a couple of weeks ago.

Hmm, I only remember George Herold's thread about function generators.
What's the subject line of the thread?

 

[Joerg]

John Larkin wrote:
Jamie wrote:
[...]
I think you'll find if you don't have a latency problem with the
serial link to the chip, you should be able to do all the FMing you
want..
The problem with the uC on these little boards is not the serial link.
Well, at least not if 100Hz sweeps suffice. The problem is that they are
too small to calculate the numbers on the fly and usually have to little
flash left to store them in a LUT. Plus that would be a major
time-consuming hack.
Fancy ramped, modulated DDS sinewave generation at 200K samples/sec would be no
sweat for a $4 ARM, and you get a mux'd ADC and a DAC for free. But yes, it
would take some code slinging.
And I'll probably do that if this becomes a product, with whatever
processor the local SW folks can handle without a major learning curve.
Just not right now, got to watch work load, expenses and time line. So
it'll be analog for now.
If you do go ARM, let me know if you'd like some example C code to butcher. We
have an app that uses an ADC interrupt to do a filtering + PID algorithm, ADC in
to DAC out, on an LPC1754. The algorithm is pretty fancy, and we run it at 100
KHz with the internal uP clock throttled down to 50 MHz. We pay $3.55 each,
pre-programmed by a distributor.
Bring your programmer and we'll go to Zeitgeist and we'll explain our code and
the DDS theory. Your treat, of course.

That sounds good. Although this project would fit much nicer into a
Cypress PSoC because that has lots of useful analog functions in there.
Like S/C filters that can be pressed into service as mixers.

I just saw the new STM32F3xx, cortexM4 with all the usual interfaces
and up to four opamps/PGAs and seven comparators

That would be nice. But ST is not on my most favored list, mostly
because of their IMHO strongly lacking customer service and screwed up
web site.

 

[Spehro Pefhany]

I wonder what's the temperature of a well-stirred mixture of crushed ice, rum,
and Coke. That deserves further research.

With a Type K thermocouple immersed in a similar ice-liquid mixture, I
get close to 0°C, but the experiment needs to be repeated with better
instrumentation.

http://www.speff.com/Dalwhinnie_test.jpg


Best regards,
Spehro Pefhany

 

[[email protected]]

Try some Ron Zacapa 23, straight of course. It makes cognac obsolete.

Indeed, I've always hated rum, especially rum and coke
then I tried a Ron Zacapa and that is damn nice


-Lasse

 

[Jamie]

I wonder what's the temperature of a well-stirred mixture of crushed ice, rum,
and Coke. That deserves further research.

For quick chilled drinks, this seems to work
http://howto.yellow.co.nz/food-drink/wine-and-beer/how-to-chill-a-beer-fast/

Jamie

 

[Spehro Pefhany]

A big thing around here is a girl with a cart who makes ice cream to order, by
whipping LN2 into cream stuff. I haven't had the luck to run into her, but I
hear it's pretty good.

They've been using LN2 a bit much for that kind of thing:-

http://www.telegraph.co.uk/health/9...nitrogen-drinks-after-girl-loses-stomach.html

It makes wine-sickles pretty easily, but they're too cold to be
comfortably consumed.


Best regards,
Spehro Pefhany

 

[rickman]

A big thing around here is a girl with a cart who makes ice cream to order, by
whipping LN2 into cream stuff. I haven't had the luck to run into her, but I
hear it's pretty good.

I bet she gets a lot of dates!

 

[josephkk]

I wonder what's the temperature of a well-stirred mixture of crushed ice, rum,
and Coke. That deserves further research.

I expect it may vary some depending on the ratios of the constituents.

?-)