OT - Electronics Suppliers

[Tekker]

Does anyone know of any good electronics suppliers online that offer free samples?

For those that saw my post a while back, we are working on building a guitar effects processor for our final project in electronics... And what we really need is a 16-bit parallel ADC and a DAC, both in a DIP package. Or we need an "in-expensive" way to expand really small packages so that we can actually work with them, there was one site that had an adaptor for $100!

We have already recieved some free samples from Texas Instruments but they are all surface mount chips and are too small to work with... One of the guys in my group actually tried to solder wires to each of the pins under a microscope... But I think he's given up on that idea! lol


I'm at school right now, and I'll try to post an update on how our project's been going so far when I get home....

-tkr

 

[Tekker]

Ok, I'm home... So it's time for an update...

We decided to use a Motorola 68HC12 microcontroller because it is 16 bit (our microcontroller class uses a Motorola 68HC11, but it is 8 bit and that just isn't going to cut it for a guitar processor), so we have a trainer board on order through the school's bookstore and hopefully it'll get here soon so we can get to work on it!

Both of the other members in my group own an 68HC11 trainer that we use for our class so we have already experimented with the 68HC11 trainer and were able to get sound going in and coming out! Woohoo!
It sounded like garbage because it was only 8 bit and the bottom half of the waveform was chopped off (the microcontroller can't read negative voltages). So we tried adding a DC reference to the input signal that would make it swing above and below 2.5V (instead of 0V) so that the signal never goes negative and the microcontroller can process it. Then just before the speakers we used a coupling capacitor (capacitors block DC and only pass AC) so theoretically the DC reference that we added should have been blocked by the cap leaving only the AC signal going to the speakers... But it didn't work and we sill only had the positive half of the signal. D'oh!

So we never got it to work properly, because unfortunately my team member toasted his microcontroller (on the trainer that we were using for our project) when he was working on another lab for our class... So we tried switching everything to another trainer (from the school) and we haven't been able to get it to work again. But at least we know that it will actually work, so we're not going to fuss with this anymore until our 68HC12 comes in.

We also have written the code for our digital delay (it hasn't been tested but it should hopefully work ) and we have two parameters (tempo and decay) that we can change using two external controls (pots).

We also have our active lowpass filters designed to eliminate all the noise and harmonics above 18kHz, but we still need to build them... We got some free op amp samples from Texas Instruments that were about half the size that we were expecting, but luckily one of my team members had expansion boards that you could solder the chip to and it expanded the traces out so that you could have more room to solder wires to it and we got those done today.

So other than that (I think that pretty much covers the important stuff) we have just been searching and searching and searching for ADC and DAC packages big enough that we can actually use (preferably DIP packages). We have ordered several free samples from Texas Instruments and some other sites, but they have all been little tiny things that we can't really use.

So if anyone knows of any other sites with free samples (or really cheap prices) we could sure use them....

-tkr