Open source PCB design

[Ran_Talbott]

Originally Posted by pcrider

The LM2940.. was designed by National Semiconductor for auto applications with attendent power interruptions and spiking and is available with a 5v output.

I just took a look at the datasheet for the LM2940, and as I read it, there's no spike protection (but, since I'm an embedded software guy, with only modest hardware knowledge, I might be mistaken). I believe the "automotive thang" was the low dropout so the 5V wouldn't go squirrelly during crank.

Back in the 1980s and 1990s, I used to do a lot of work with a friend who is a real EE, developing systems for (mostly automotive) engine control. The power input circuit he always used (with great results: he had pretty near zero units get smoked in the field) was:

1. A series diode (to protect against reversed wires during installation, and negative spikes that can occur in some vehicle electrical systems). Any old 1N4000 series will do. Since I'm not personally building a million of these, I'd spring the extra 2 or 3 cents, and go for a 1N4003 or better: it's cheap insurance.

2. A series resistor to help absorb spike energy, and dissipate some heat instead of the regulator doing it all. About 10 Ohms, since the MPGuino peaks at about 200mA.

3. A 1/2W Zener in the 25-30V range.

4. An input filter cap. The 330uF already specified might be okay, but I'd probably go for a smaller one, and use a tantalum (there are some formulas around for picking the value). Make sure its voltage rating is similar to the Zener's, since it will have to absorb spikes of up to the Zener voltage.

The output from this network went into an ordinary 3-terminal regulator (like a 7805 or an LM317).

Maybe the newer vehicles that most folks are building for have cleaner electical systems, but I wouldn't think of putting even a $40 MPGuino in my old-enough-to-vote vehicles without this sort of circuit.

Ran

[dcb]

Ok, I ordered some PCBs, hopefully in time for Christmas Been wanting to try this manufacturing thing for a little bit.

Here's the latest layout, has extra capacitance on the supply line and on the crystal and optional vss pullup/pulldown resistors (for noisy reed switch cars). Also went to 50k ohms. Will try it out and put some units together if it works.

[scubascooby]

Hi DCB,

I'm quite new to this mpgUino project. I think my soldering and building skills are up to it but I want to build a small neat unit that doesn't look too homebuilt so this is good news for me.

[meelis11]

Originally Posted by dcb

Ok, I ordered some PCBs, hopefully in time for Christmas Been wanting to try this manufacturing thing for a little bit.

Here's the latest layout, has extra capacitance on the supply line and on the crystal and optional vss pullup/pulldown resistors (for noisy reed switch cars). Also went to 50k ohms. Will try it out and put some units together if it works.

Hi DCB!
good work!
Is this layout still latest PCB? Is it possible to get Eagle file for this PCB?

Sorry for stupid question, but that power supply part looks strange - near IC2 voltage regulator, there is C3 capacitor - shouldn't it be between two upper pins (Out and Gnd) on IC2 rather than Input and Gnd?
I looked this layout about 20minutes and still dont figure it out why it is like it is - all other places in internet (breadboard arduino) that power supply part is differently.
Can you comment this please.

Meelis

[williamson]

To "MilesperTank": Have you thought of designing an open-source DC to DC converter for an electric car? 144 volt in, 14.5 volts out. Maintenance-free batteries are charged to 14.5, not 13.8v. Measure any car. In fact, anyone running a DC to DC converter (purchased) at 13.8 volts may find poor battery capacity. (90 amps out would be nice.) I am also an analog designer, and I could design and build the (massive?) power transformer.

[rkhanso]

Originally Posted by meelis11

Hi DCB!
good work!
Is this layout still latest PCB? Is it possible to get Eagle file for this PCB?
Meelis

meelis11, I think this may be the answer to your question, though I'm completely new here (first post)

I realize that the layout above was posted quite some time ago (2 years), but...
also wondering if there's an update, or is the information, schematic, PCB at THIS website current?

I really like the idea of it being so small, with the LCD on one side, the PCB on the other. Very nice.

[dcb]

here is the latest schematic for the prebuilt: (note: I'm using a 20mhz crystal, not 16, and the zeners are both 5.1 volts, and I'm using an atmega328 currently and not a mega8), more descriptions here, i.e. switched to npn transistor for lcd and I don't try to keep the backlight running if the power dips.
http://ecomodder.com/forum/showthrea...tml#post171793

[rkhanso]

Originally Posted by dcb

here is the latest schematic for the prebuilt: (note: I'm using a 20mhz crystal, not 16, and the zeners are both 5.1 volts)

With that "latest schematic" - does it come with a "latest PCB layout/design" or still use the one from here -->> opengauge.googlecode.com/svn/trunk/mpguino/
? Or...shall we use Eagle to generate a new PCB from this updated schematic? (my Eagle skills are non-existant)

[dcb]

I added MPGUINO13 eagle files to the repository, though a couple things to note:

It is not compatible with the working but deprecated arduino pde. The original MPGUINO files and schematic should be though. Arduino is a great learning platform, but I had really pushed it beyond arduinos meta-limits here and it wasn't sustainable (hence the arduino version 0011 dependency)

It is only compatible with mpguino.cpp version .83 and above (just released .86 with metric display option which needs an atmega328 for space), so you will need to sort out making hex file and isp programming.

It is not single sided, turns out that none of the board houses offer any price break for single v/s double sided so I lost interest in maintaining the extra complicated one-sided layout. If you just need one, I suggest other prototype construction methods, i.e. what is in post 15

[spitsnrovers]

Great advancement! I've been waiting for the KM/L (L/100Km) possibility.

I don't understand a lot about the details you've posted, but am certainly interested in tackling it, as are a couple of others of us "north of the border".