Puma board for FreeEMS

[jharvey]

it's not a mix of modes but it a mix of pins between the package shown in the data sheet and the SOIC package.

To me it appears that the FB pin may have a problem. I'm a bit ignorant about exactly what the FB pin does. Seems the reference schematic's will either connect it to Vout (allowing an analog output) or to a pot wiper that ranges from Vref to gnd (allowing for a digital out at a set point). As drawn, it's hardwired to Vref, which the wiper will allow. This seems to put it in "set point" mode which I think will cause the output to go low when just under 500C and go +5 at just over 500C. However it may induce an offset instead, such that the full scale might not require the 12V supply. I believe it will want to be connected to that 12V. I guess time will tell. I feel the datasheet is vague relative to the FB pin. If worst comes to worst, lead 5 can be lifted and have a wire soldered directly to it. Also the 5V line can be broken and attached to 12V via jumper if required. Perhaps Macro's will want to lightly drill the top of the via under the AD597 chip, breaking the 5V supply trace. It's easy to break this connection before the chip is installed, but will require removing the chip after it's installed.

I'm looking at an 8 page datasheet. Perhaps there is a better datasheet or app note? What I'm looking at seems cramped and not very clear.

[jbelanger]

FB is wrong, 5V is wrong and the output is wrong if you put 12V (to have more than 500C) because it'll have up to 12V. Also, you want to ground the chromel input through a resistor (dotted line in the data sheet).

The data sheet is not very clear but I've seen worse.

Jean

[nitrousnrg]

That was such a stupid mistake. The mcu vcc's and reset pins, ok, fb maybe, but missing the 500° limit is sad. And, the board doesn't have a stable 12v supply. Maybe a well filtered Vbat and a divisor in the output is enough. I'd try it if I had the part.

When I wanted to order the component to digikey, it was on stock but when I confirmed the order, the page said "call" (it didn't say "call" before). I don't know what is the deal with that component, I didn't call, but did choose in the rush another thermocouple IC that is only the cold junction compensation.

About the 50+ schematic pages, they're perfectly fine in kicad if you browse them. I'd like to see some html code to display them in browsable fashion. Kicad can plot every page as svg, for example. Hierarchy relationships must be somewhere in the sch file. The position in the page of the subschematics is defined in the files too. The parsing doesn't seem too difficult, but I don't know html well enough to generate it from a script. I think kicad-dev would be interested in this.

Thanks for the spotting jean!

[jharvey]

It appears didikey has a pile of them

http://search.digikey.com/scripts/dksea ... D597ARZ-ND

On a good note, Marcos tossed it in there as his own preference, and it's not a critical sub circuit.

[edit fixed typo, Marcos was Macros]

[nitrousnrg]

lol I'm Marcos, I thought it was a typo :p No worries.

yes, digikey always had it in stock. You can add it to an order without complains, but when I was about to pay, all the components were ok except for the ad597, which had a "call" link.

[Fred]

EGT is an output condition anyway, and totally non-essential. I would race your fiat+egt against my mazda without any day ;-)

Re the stable 12v, you'd need a switching reg to achieve that, wouldn't you? It's only going to matter when the engine is up to speed, and the alternator is humming ,so perhaps a stock 12v reg down from 14.4 with brownouts on startup would suffice?

Fred.

[tpsretard]

i would not say it was non-essential.
it is not needed right away, but for later additional features i would say it would be nice to have

i have some engines that run egt feed back, 13:1 cr and 70 psi of boost at 3,000rpm running very lean and absolutely ubserd timing means things can get hot. (it is a WRC engine btw, not a dream)

[Fred]

Sure, but even an engine with 250hp/litre specific power doesn't NEED it. Hence non-essential for the majority of people. WRC engines are not the majority ;-)

[Fred]

Plus, the context here is a first cut board, not targetted at anything specific except the Argy "tuning" market.

[tpsretard]

that is why i said needed right away

you would not like my dayly driven engine then, lol