Puma board for FreeEMS

[nitrousnrg]

Ahhhhh, so you've gone with MASSIVE OVERKILL as a temporary thing for driving externals. What type of fets are these? Auto or otherwise?

I've chosen the fets just a few hours ago. A cheap TO220 would cost $0.7, these costs $1.09. A TO92 would suffice, but I don't care about $1 extra if I can narrow a little the components diversity. For those who are assembling the board: power transistors are mostly up to you.

There are 7 RFP30N06: 4 for ign, 2 general purpose, 1 fuel. That makes $7.63.

The datasheet says:

They (RFP30N06) were designed for use in applications
such as switching regulators, switching converters, motor
drivers and relay drivers. These transistors can be operated
directly from integrated circuits.

So, although I don't read the word 'autofet' they behave in similar way. Digikey tagged it as a 'logic gate' mosfet. Also, most of the data is based on 5v Vgs tests.

I'd like to be able to drive coils directly, but I won't test that now. Who knows, maybe I change my mind and get rid of all those TO220.

Also, if they're for driving ignitors then it's possible that a pull up will be required (assuming fets pulling to ground when on). Do you have that in place?

Um... no. You mean in the drain side? I have a selectable pull up/down on the gate side, thats what the XOR gate is for. Nothing in the drain, though. That could fire the coils... Its one track and 4 resistors, I have to add them.

ASSUME???? Are you designing this or guessing it? :-p Assume nothing.

Ok, but you'd have to change the planned Puma release to 2019 ;-)

As far as the power pins - let's just say that I am "experienced" and not that smart (I did almost the same thing on my design).

Lets say its very overlookeable... Its my second mistake about the VDD pins.

the input signal has to go through the resistors and then is "clamped" to the power supply rails of the MAX part

Oh, good point. Chacking the datasheet, inputs are clamped to VDD, so the resostors have to stand a lot of voltage and up to 40mA.

[jharvey]

This may be a time to take advantage of KICAD's text file format. The schematic files in KICAD are simply a text file. This means one can open the source schematic files with notepad, nano or what ever text editor, then modify it, and open it with KICAD. Assuming you haven't made a mistake and corrupted the source file, KICAD will open it. For example, in ignition3.sch we see R29 has an associated Newark and Digikey part number.

Code: Select all

$Comp
L R R29
U 1 1 48AA2523
P 3300 1650
F 0 "R29" V 3380 1650 50  0000 C CNN
F 1 "3.3k" V 3300 1650 50  0000 C CNN
F 2 "R4-SM0805" V 1980 1650 60  0001 C CNN
F 4 "newark,38k0340" V -120 2400 60  0001 C CNN "Field1"
F 5 "RMCF0805JT3K30CT-ND" V -120 2400 60  0001 C CNN "Field2"
F 6 "vendor2, thru w hem" V -120 2400 60  0001 C CNN "Field3"
F 7 "vendor2, smd w hem" V -120 2400 60  0001 C CNN "Field4"
F 8 "1/4,W" V -120 2400 60  0001 C CNN "Field5"
F 9 "5,%" V -120 2400 60  0001 C CNN "Field6"
F 10 "carbon film" V -120 2400 60  0001 C CNN "Field7"
F 11 "other,more,stuff" V -120 2400 60  0001 C CNN "Field8"
	1    3300 1650
	0    1    1    0   
$EndComp

Ug, that's old, and if I were do to do it again, I would recommend changing the properties a bit. One issue I've seen on another project, was a vendor substituting a part. In one case Digikey claimed they couldn't get the correct part from the vendor, so they gave us a similar cap, but different construction technique. This didn't work in our case as the construction style was critical to the bandwidth of the filter it was part of. So I would recommend a property setup similar to this.

Code: Select all

$Comp
L R R?
U 1 1 488E4A25
P 9350 6600
F 0 "R?" V 9430 6600 50  0000 C CNN
F 1 "2.7k" V 9350 6600 50  0000 C CNN
F 2 "SM0805-R4" V 9530 6700 60  0001 C CNN
F 4 "vishay,CRCW08052K70FKEA" V 7180 8000 60  0001 C CNN "mfg,#"
F 5 "newark,52K9964" V 7180 8000 60  0001 C CNN "vend1,#"
F 6 "-,-" V 7180 8000 60  0001 C CNN "vend2,#"
F 7 "-,-" V 7180 8000 60  0001 C CNN "vend3,#"
F 8 "125,mW" V 7180 8000 60  0001 C CNN "power,mW"
F 9 "1,%" V 7180 8000 60  0001 C CNN "Tolerance,%"
F 10 "thick film" V 7180 8000 60  0001 C CNN "construction"
F 11 "other,more,stuff" V 7180 8000 60  0001 C CNN "misc"
	1    9350 6600
	1    0    0    -1  
$EndComp

Because these are text files, a script could be drafted that would parse each file, looking for F 1 "2.7k" When found, it can blindly copy the F 4 line, then copy a block similar to above lines F 5 thru 1 0 0 -1 then it could copy $EndComp until it again found F 1 "2.7k" When done you would have the same file as the original, but with the property block for all 2.7k's changed. This could be done I guess up to 50 times for each component, and then the BOM's and ref designators can be created from the BOM creation tool.

My scripting and programming skills are marginal, anyone up for the task? A script shouldn't be that hard in a posix environment, or with Python. I have a shell script around here somewhere. I can find it then offer that as a draft if someone's interested.

[nitrousnrg]

Cool, thats how you did it!

I was guessing you've created a library of custom resistors, capacitors, etc, which seemed like a lot of work. This has much more sense. Spin2 needs it.

Also, kicad's .lst files were so different to those needed by digikey that I almost write a script to format them accordingly. Fortunately I found the option to format it in a more similar way, but it still isn't the right format, though. A little program should make a proper digikey BOM from kicad's .lst.

When I have the time, I'll try to automatize the components and BOM genereation. A little app could do that, and kicad-developers might like it too. Of course, if there is someone keen over there, he/she is most welcome.

[Fred]

Fortunately I found the option to format it in a more similar way, but it still isn't the right format, though.

Either but, or though, not both! :-)

(in case anyone is wondering, I'm not an arsehole, Marcos and I have a Spanish-English exchange deal going on...)

[nitrousnrg]

Oh God, a pretty nice (awesome for an argy) donation has been done for supporting the board development.

So good, its going to speed up the develeopment a lot. I can place a digikey order without crying while converting dollars to pesos.

Tomorrow is the first TBDML day in a long time. Lets hope TBDML construction don't last for too long :-)

[nitrousnrg]

Those who are going to build one from scratch may wanna take a look a this thread for a way to load the serial monitor.
viewtopic.php?f=37&t=1000

Also, I'm wainting for the PCBs, estimated delivery: 13 Jan 2011

[Fred]

Marcos, once they arrive, could you start a new thread for assembly and testing of Spin 1 specifically? We can copy/paste content from it into the Spin 2 thread and so on until we have a finalish version. This section is fine for all such threads.

[jharvey]

I seem to recall the PCB's can show up any day now. Once you get them, what's the first steps? I'm guessing tossing them on a flat bed scanner and posting some pics will be in order. Such that we can do a visual. How long do you think it will be before you have verified you can program them and that they don't go up in flames?

[nitrousnrg]

I seem to recall the PCB's can show up any day now.

Estimated delivery (from fedex): 13th Jan

I'm guessing tossing them on a flat bed scanner and posting some pics will be in order.

Of course!

How long do you think it will be before you have verified you can program them and that they don't go up in flames?

Um...if I'm free and get manly enough to solder the MCU, 3 or 4 days. That would be only to make sure nothing blows up. The ultimate "blinking led test" depends on my bdm pod. I could finish it before the PCB delivery.

[jharvey]

I know there is a real place to post this, but I can't find that PCB mfg thread, so I'm posting it here.

http://www.aapcb.com/assembly.asp

Probably good to compare prices against thier noted assembly prices.