Puma board for FreeEMS

[nitrousnrg]

Today I finished the BOM, and this is the result of my digikey quote:

56 different components, which cost $180 for the complete setup (wow, not cheap at all).

Nevertheless, if you don't use the P&H circuits, the cost drops by $57
Thermocouple driver can be avoided (-$4.3)
AAP sensor too (-$14)
MAP sensor too, if you already have one (-$14)
stepper driver (-$6)

So, a basic spin1 cost around $100 + pcb. + assembly + shipping.

This is for one board, buying bulk the costs per unit go down.

[Fred]

56 different components, which cost $180 for the complete setup (wow, not cheap at all).

Just to be clear, 56 different types of components, or 56 components total?

Nevertheless, if you don't use the P&H circuits, the cost drops by $57

Does this included replacing them with autofets? Or not doing fuel at all? What are the details on a per channel basis. Many will only want 4 autofets = 20usd or less.

How much do the horrid internal ignition drivers cost? I won't use them.. and nor will anyone that takes my recommendation seriously. Spec the saving there, please :-)

Fred.

[nitrousnrg]

56 different components, which cost $180 for the complete setup (wow, not cheap at all).

Just to be clear, 56 different types of components, or 56 components total?

56 different types of components, near 400 componets total.

Nevertheless, if you don't use the P&H circuits, the cost drops by $57

Does this included replacing them with autofets? Or not doing fuel at all? What are the details on a per channel basis. Many will only want 4 autofets = 20usd or less.

How much do the horrid internal ignition drivers cost? I won't use them.. and nor will anyone that takes my recommendation seriously. Spec the saving there, please :-)

Without any kind of injector drivers. Add those $20 for 4 autofets :-)

[nitrousnrg]

How much do the horrid internal ignition drivers cost? I won't use them

Right now, I put 4 normal MOSFETs for ignition, just to drive external ign drivers. All mosfets are the same (ign, fuel, 2 PWM), to ease the work of a P&P.

[TonyS]

Hi nitrousnrg,

It might be helpful if you could provide a costed BOM (w/ ref designators) to aide in this discussion.

Also,
I took a quick look at your schematic and found a few opportunities to reduce smoke generation : ).

The VDD1, VDD2, and VDDPLL pins should not be connected to +5V. There are internal 2.5V voltage regulators associated with these pins and only bypass caps are to be connected to them (see pg 66 and 1295 of the data sheet).

The 10k resistors on the inputs to the MAX9924 are physically too small (0805, 125mW?). Quite a bit of power can be dissipated by these parts at higher VR input signals. The MAX9926 Evaluation Kit documentation actually mentions that the two, 5k, 1206 size (250mW) parts (in series) used on in the kit may not be enough under certain circumstances.

Thanks

[nitrousnrg]

wow, you're so right about everything!

Thanks a lot, I owe you a MCU! I assumed VDDx and VDDPLL were connected somewhere to 5v. Oh god, so close, thanks a lot.

About the MAX, I always taught those resistors were small, but not by that much!

I guess you can have up to 140v between the VR sensor terminals, and the MAX992* input resistance is 100k.
That doesn't allow much current to flow through the resistors, I wouldn't expect more than 150mW of power being dissipated. Anyway, if the eval board has such resistors, I'm adding them for the next spin. Spin1 can use big normal resistors in series, somewhere :-) I'll test it as it is.

The latest BOM is on github:
https://github.com/nitrousnrg/puma/raw/ ... %20BOM.csv
hit "raw" to download the file.
I'm uploading the BOM to puma.freeems.org when Fred gives me ssh access(you hear Fred? I could bring this up on every post... muahah)

Thanks again Tony :-)

[Fred]

How much do the horrid internal ignition drivers cost? I won't use them

Right now, I put 4 normal MOSFETs for ignition, just to drive external ign drivers. All mosfets are the same (ign, fuel, 2 PWM), to ease the work of a P&P.

Ahhhhh, so you've gone with MASSIVE OVERKILL as a temporary thing for driving externals. What type of fets are these? Auto or otherwise? If otherwise, I see no drivers for them. If you intend to keep them as predrivers, smd stuff would have been plenty grunty enough. If not, and you just plan to sub parts in the BOM, then it might be a bit misleading/vague in future when the plan changes. I guess this is just spin 1, though, so we can correct that before going further. How much are they in the BOM, in any case, as they can come off my price estimate :-) 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?

Huff!!!! (I had to look at your email to realise what you meant, but I should have known!) Nice to see you on here, esp giving good information on the design like that! :-) Excellent! :-)

Can I take this to mean that you'll be FreeEMSing your son's DSM?

Marcos, see post in other thread any second now...

Fred.

[Fred]

Ingles y philosophy time!

Thanks a lot, I owe you a MCU! I assumed VDDx and VDDPLL were connected somewhere to 5v.

About the MAX, I always taught those resistors were small, but not by that much!

"an MCU" - em see you first sound is vowel, so an, not a.
thought not taught.
ASSUME???? Are you designing this or guessing it? :-p Assume nothing.

Huff, thanks again! :-)

Fred.

[TonyS]

Hi Fred,

No FreeEMSing the Eclipse as one of my son's friends rear-ended it so he won't drive it anymore. Insurance paid for 2/3 but I am trying to sell it for the remaining 1/3 (runs and drives, just ugly).

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).

I am not entirely sure why the resistors on the VR circuit need to be so big in a differential application, but in a single-ended application, the input signal has to go through the resistors and then is "clamped" to the power supply rails of the MAX part (say 60Vrms across 10k = 360mW). Not really sure either way, just know that the eval board uses big parts.

Tony

[Fred]

Bummer about the DSM :-(

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).

LOL, fair enough, I like the honesty, it made me laugh :-)

Fred.