Puma board for FreeEMS

[jharvey]

I decided to focus on the smaller changes and do the larger changes last. I know PUMA isn't intended to be as flexible as DFH, so perhaps this can simply be one of those limits. If not, I don't see why we can't change the regulators later down the line. I'll wait to see what the empirical data shows us.

I know the FTDI chip can't do a wide temp range, perhaps we should simply limit the max temp of the ECU. I seem to recall our expectations are that this to work at well over 38C (~100F) and empirical data should verify how much hotter it will be able to go. Once we toss it in a stove and stress test it, we'll know for sure.

Hmmm, that attempted EGT might work as a regulator over temp sensor.

Any how, I have rolled back the top level schematic such that it calls out for the regulators on spin1. I have started a couple of the changes, and should be able to do more this evening. As far as I can tell, there's plenty of space for upgrading the regulator at a future time, so I don't see a need to do that now.

Also, on the SMT USB connectors, how much stronger would it be if the SMT pads included a VIA and had solder that went all the way through. Perhaps on the test you just tore off, you can drill a small hole and make hacked attempt at testing the via idea.

[TonyS]

I would like to help (if I can) with some of the issues being noted for this first pass board. Can you tell me where I can find an accurate / up-to-date schematic of this board (in pdf format)? The one I currently have is older. Thanks
- Huff

[jharvey]

I guess that depends. Are you looking for the schematics and layout for what was send to the MFG? Marcos and I have made several changes after it was release for MFG. For example, the schematic didn't have the component properties populated, which wasn't require for spinning the board, but is required for populating the boards. After it was released, I wrote a script that filled in most components, but there are still some that need to be filled in. Also there are components that need to change, ect. The PDF you have is likely the PDF from when it was released. I have a KICAD copy in github, that's the most up-to-date, but I haven't made a PDF of it yet. Are you looking for a PDF of that copy?

Do you have KICAD skills? If not, are you willing/interested to learn?

[jharvey]

[edit]The below links were temporary, and do not exist any more. This is post was left for historical purposes[/edit]

I just added a tempory PDF found here
https://github.com/jharvey/puma_JAH/blo ... ematic.pdf
and the layout found here.
https://github.com/jharvey/puma_JAH/blo ... 0Print.pdf

[nitrousnrg]

Fred, IMO 4 cables for Vbat is totally unnecesary. Having a cable for power and another separate cable for the digital stuff already put us in the safe side.

About the reference, if you wish it that way, ok. I don't like it, but its up to you. Voltage drop in the low power vbat cable shouldn't be noticeable. You already have almost a 1% error in the resistor divider, Vref = VDD = not accurate, and the 5v for the analog circuitry has a 2% tolerance, much better at 25°C but still...

Today I checked Motec's ecus, they have only one wire for Vbat, and 2 for gnd. And those controls 8 low Z injectors, up to 6A each. The cables have 3.3mm wire, which is reasonable. Using one 3.3mm wire for power-hungry stuff, and another 3.3mm wire for ICs, circuitry and the reference is enough for me. If a $6k ecu uses only 1 cable, I'd think it works pretty well.

Tony, jharvey is right, spin 1 can be seen in any of our github accounts (there is a spin1 tag in the branch). The latest mods are in Jared's repo. I encourage you to install kicad, its very easy to go through the design sheets :-)

Jharvey, reading through the regulator datasheet, I see it has a better ripple, *in the internal regulator*. However, the output ripple depends on the filtering circuitry. I'll keep reading to find if it is better than the actual regulator (20mv typ for line regulator, 35mVtyp for load regulation). If the new setup proves being better, I'd like to implemented it for spin 2. If that cange isn't implement now, it won't be implemented this year.

[jharvey]

My take on it for now, is that we should make mild changes to this branch. Then when the time comes, branch it and add the enhancements to the new branch. This spin is good for a specific category of vehicle.

I seem to recall the values don't match exactly what the datasheet might indicate. A simulator from the below link obtained the selected parts.

http://www.st.com/internet/com/software/simulators.jsp

I'm going to go add movex's design now and take a closer look at it. One thing I wonder is what happens when you disable with the disable pin, does it trickle or not....

[TonyS]

jharvey - Yes, I currently am most interested in the schematic for Puma 1 - as built. Thanks for producing the schematic / layout pdf's.

I really don't want to install KICAD (and become familiar with it) at this point just to view the schematics for this board. In the future I may, as I like to "review" designs by cross-probing schematic / layout (I assume KICAD has cross-probing functionality).

Thanks
- Huff

[jharvey]

KICAD is really useful for viewing as well. For example, open both the schematic and the board layout. Then click the component you are looking at, and then switch to the schematic. It will put the cursor on the sub circuit and component you have selected in the board layout. Same thing the other way. Click on the schematic, and it hight lights in the PCB file. If you have 2 screen, it becomes a real wow factor. The pdf's on puma.freeems.org are the most accurate to the boards that were MFG'ed. What I posted on git has several changes. Smallish changes, but changes anyhow. Also that PDF will probably go away on my next check in, so get it while it's hot.

[TonyS]

I don't think the schematics / layout on "puma.freeems.org" are the most accurate as they show the incorrect power connections to the uC that were pointed out (and hopefully fixed) before the blank pcb was made.

The schematics / layout on "git" show this as being taken care of.

So is there an accurate schematic for THIS board?

[jharvey]

About the regulator, attached is the file I have been dubbing with at stmicro. The specs are 6v to 16v input, 5v output .1% ripple (~5mV ripple) 85/90% eff, 1 amp. I then selected components using the largest suggested inductor, such that most of the energy is stored in inductance, which I guess is good for temperature stability. Then I looked for a single cap design, single cap tant for assembly ease. Then I chose the lowest voltage drop diode, to minimize the heat dissipated by the diode.

Then I decided to find if the suggested parts are available. Ugh. Those part didn't have vendors, let alone digikey/newark/ect vendors. So I'll have to rake down the list looking for each component's availability, then once it's found, do the next component, ect. I have to step away for a bit now, perhaps I can jump on it tomorrow morning. If someone else gets a chance to rake down the parts feel free.

Hmm, apparently .prj extensions aren't allowed, so I zipped the file.