Don't be a tease, give me a squeeze!

This discussion should continue here

@pichenettes I’ll be interested to know how you deal with the whole patch/multi setup thing with the new polysynth. I’ve always found this to be quite awkward on all the multitimbral polis I’ve used.
I’m assuming it’s going to be multitimbral, from the first demo there.


For those who haven’t already noticed it, this set just appeared on Soundcloud.


Holding my breath…

@pichenettes thats luke warm in my book :slight_smile: That MB6582 pictured above pulls a whopping 700 mA just on the SIDs alone

These are good for audio since the switching speed is high so any noise they make is usually inaudible.

Cool (literally)! There’s enough room for those, so it could be an emergency solution… On my project, they are not as stressed as much as on the MB808… The current drawn on the +5V rail is 310mA ; so with a voltage 7.5V drop (9V AC) we have less than 2.5W to dissipate. The current heatsink I use has a 16°/W resistance. I still wouldn’t keep my finger on the vreg :slight_smile:

23x22x7.6. They come in vertical or horizontal versions (just different pins). If you gave enough room for a heat sink, it will fit easily. Amazing devices though, I did a bunch of tests comparing them to 78S05s (the 2 amp ones) and with a 18VDC input and a 2 amp load the damn thing does not even get warm. The 78S05 got so hot that I could feel it on my face 3 ft away and shut down shortly there after in the same test

@altitude, if you have a PT78ST105H lying around, could you please tell me its dimensions?

There are several 78xx pinout compatible drop in switchers out there. Not exactly cheap but they work like a charm. I use the Power Trends PT78 all the time on projects that have heat problems on the 7805 (MB808 is the worst, 21VDC input, you can feel the heat coming off the vReg outside the case)

I think it’s a bit late to explore this option :slight_smile:

As for the 5v power supply and smell of burning plexi : would a 5v SMPS be overkill?
Of course there are concerns about the ripple, and the components need to stay through hole and easy to find. I’m thinking more precisely about components such as the MC33063 that’s been around for several years already, seems to be reliable and easy to find, but it might require extra space on the board. Or, a more recent thing such as a TL2575 (available as a sample by TI, I haven’t looked yet if it was easy to find by regular component sellers).

Today, I managed to get a PIC to talk to a Dallas RTC. I am officially in the Cretaceous period. When will my life ever have meaning?

I think my solution to the problem will be to buy SD cards in bulk from a respectable source and sell them with the kit. Possibly pre-formatted and populated. I say that but I have no idea how annoying it’ll be to image them one by one :slight_smile: Can’t be worse than eeproms…

Seems like Christmas will be early this year…

The next problem will be SD card brands or fake SD cards :slight_smile:

Sandisc are fine I’m guessing?

Ive just stopped buying sd cards from ebay or china, only way it seems to not get lemon sd cards.

Are you sure you’re not confusing midsummer with Christmas? :slight_smile:

Thanks for the update!

With the MS20+Delay board out of the table (literally), I took myself the day to look into the remaining bug.

The bug was the following: with a SDHC card loaded into the unit, the unit boots but the SD card incorrectly reports itself as not being SDHC ; and this confuses the filesystem code which will use byte offsets (SD standard) instead of 512 bytes sector offsets (SDHC standard) ; and I need to hook up a logic analyzer on the SPI bus to see that O_O. I have failed to reproduce it in normal conditions over more than 60 power on/off sequences ; and managed to reproduce it only in the following setup: AVR programmer hooked up to the unit, fast power off/on cycles and resets (which is my normal setup, not yours :D). So there’s a good chance the problem was either due to the programmer adding extra load or capacitance on the SPI bus ; or to short glitches on the SD card power supply due to the repeated power cycles. I really hope it is since it’s hard to find non SDHC cards. Every now and then I hook up the unit and do a few cycles of tests. So far so good.

I get the hopefully final PCB tomorrow and will build it in the next days. The last issue I had to address is the input voltage dilemma. My initial shot was 12V AC - does not need super big caps on the rectification end, and even if there’s 1V pp of ripple on the “rectified” voltage, it stays above the headroom for the regulators. The problem is the smell of burnt plexi in the neighborhood of the 7805 heatsink :smiley: So I’ve switched to 9V AC, which works most of the time but not always, as some 9V transformers have an output voltage which is a bit lower and the rectified voltage dips below the 2V or 2.5V headroom required by 78xx. This adds a bit of 50Hz hum on the audio output. My final solution is to use modern regulators (LM2940s) instead of 78xx to require smaller input voltages. I just hope they will stay stable enough.

I’ll let you know how it goes and unveil the whole thing if it passes all tests. I’m confident it’s almost done.