Laying out my own PCB - what 'options' are useful?
 

I'm going to lay out my own MPGuino board but was wondering if anyone had any improvements that they've needed to make that I should consider in my board?

- conditioning of the VSS or injector signal (selectable pullup/pulldowns, feed through a comparator, etc)
- input power conditioning
- USB port like what FL used to include
anything else?


Anyways I thought I'd solicit input from you all on any things I should consider adding/improving on the design.

TIA,
Dave

Schematic is done for just the 'plain ol vanilla' version. Will try for a single sided board this weekend so I can etch it myself.

Answers and Questions..
 

Hi,

A really handy additional option would be an incline meter
to know when you 'should' coast down a hill. For manual
or stick shift of course.

btw, how does one make their own PCB? I really want to
know. I found freepcb and tinycad. to make gerber files.

But what is the best way?

I like using a sharpie or a laser printer for individual pcbs, but double sided has to be lined up just right and all need lots of drilling/etc. So I usually use a prototype construction method, a-la deadbug or veloboard If you are just making a couple, that is the quickest/most cost effective route, or start with an arduino.

the veloboard version actually had a connector added for a bootloader controlled reflash/comm using rs232 or ftdi cable.

I do the layout on the PC, laserprint onto vellum and use that as a mask to expose onto a pre-sensitized PCB. Then develop, etch and drill. I've done 7mil line/clearances. Pretty handy to be able to whip out a prototype that way. For my 2 sided boards I either use 4PCB.com $33 special in the US and for large quantities an offshore board house.

I don't think an inclinometer would work well as roads themselves undulate and there would be so much measurement noise from the josling car. The instantaneous MPG meter and your speedometer together should tell you when you're coasting, no?

Anyways, think I'll include a comparator/buffer on the VSS and injector input so if needed I can add some hysteresis.

re metro vss, thecheese429 JUST got a gear sensor working for a vss, you might look in that direction if the reed switch proves challenging. there are existing buffers/tweaks for noisy reed switches, so not sure you want to "fix" that till you see if it is broken.

here is the solid state vss thread:
http://ecomodder.com/forum/showthrea...tml#post178770

Thanks but I'll be doing a PCB and might as well have it in there though I may not stuff the comparator. Thought about what I'd do if I find my VSS signal is flakey - might put a hall effect in the speedo if the reed output is totally unuseable.

Decided to just do SOMETHING. Can always make another board down the road.
This version is just plain vanilla. The only difference is I brought out the RS232 lines.
Hope to have this wired in next weekend - work gets in the way of having fun.

Here's the etched board.
http://www.dschmidt.com/images/mpguino/Etched.jpg


Here's the partially stuffed board installed on the LCD. Some SMT stuff on the back for convenience. Regulator is at the bottom if I decide to bolt it to a case to heat dissipation. Should be enough room for a small heatsink.
http://www.dschmidt.com/images/mpguino/Rear.jpg


Front side view - the rear board is the same outline as the LCD.
http://www.dschmidt.com/images/mpguino/Front.jpg


I was going to use a slimmer LCD (has 2x7 terminals on the side instead) but I'm pretty sure it's an older one that takes 150mA just for the backlighting. This one is < 20mA.

really cool.. of course..
 

Yeah, its really cool.

Exactly what I'm after. How do you do pcb's like that?

I'm just a computer guy and have no idea. Do tell...:rolleyes:

- PCB software to do the schematic which then drives the layout of the board. There's some free ones out there.
- Laserprint artwork onto vellum to be used as a photopositive
- cut pre-sensitized PCB blank to size, remove the plastic film, put the artwork on top, sandwich it in a frame and expose the board through the artwork using a fluorescent lamp. Boards are pretty cheap. I bought 6" x 10" for I think $6 a board years ago that I'm still using.
- develop the board
- etch the unwanted copper off
- drill, then stuff.

Exposure has to be experimentally developed. My time is 14.5 mins.
Develop is ~ 5 seconds, or until emulsion clears fully
Etch is ~ 8 mins

Drilling is the biggest problem if you don't have the carbide bits on hand already.

Note that laserprinters are not exact in X and Y so long dimensions can walk off on you. My HP4100 is pretty good, my HP4+ I had before was worse.

cool
 

thanks for the explanation.. I've never done it before but now feel encouraged to try.

There are other methods. One is to laserprint onto special (or not so special) paper, then iron it onto a cleaned PCB to transfer the toner to the board. Soak in water to remove the paper, then etch the board. The toner is a etch stop.

I've never gotten good at that method. The nice thing about the photo method is it's easy to crank out another board, or many boards, with consistent quality.

I'm going to put a socket on my LCD instead of hard soldering it to my board. This will be a test bed and I suspect I'll need/want to take it apart and change component values.

Programmed the chip, installed it this past weekend.

Today was the first day of driving with an MPG meter in my face, and boy was it a learning experience.

Taking off in each gear I learned something that wasn't obvious to me before - higher gears get better gas mileage!
Seems obvious but I discovered it a different way. Watching the 'instant' MPG readout, if I hold the gas pedal steady at about the same throttle position in each gear, the MPG is ~ 7-8 for 1st, 15 for 2nd, 24 for 3rd, etc. This is when the engine is loaded and not just cruising in a gear. Thought the MPG in 1st and 2nd was low until I figured out why. Duh!

Found that drafting works! And I don't have to be that close to the trailer in front of me.

Coasting, even at low low speeds, gives me GREAT mpg's! Coasting in gear I can see the injector cutout working as the MPG meter registers 99999 when it happens.

Slight inclines up and down in the road, slight throttle changes, all are reflected in quite large instant MPG changes.

Drove a LOT mellower today - trying to see how high I can get the MPG up on this tank of gas. Don't know if I'm calibrated yet but regardless this device is working and giving me instand feedback on my driving.

Display is easy to read even in reasonably direct sunlight. I'm using a STN (supertwist) display so the characters are crisp and dense and has a wide viewing angle. Trippy to look at it when the sunlight is coming in as the characters are hovering on a clear piece of glass.

Just refilled the tank. 51.8 MPG on that tank - best ever. Lots of drafting, lots of coasting whenever I could. Still have lots to learn on how to get the best gas mileage.

My best before this was 48.3 MPG and that was with 12" tires and original brakes/knuckles, but average was more like 46MPG.

Best after my brake/knuckle/13" tire upgrade was 45.5MPG, but average more like 44-45mpg

Satisfied with the operation I redid the PCB layout, cleaned it up a bit and put a terminal block on for wire attachment.
http://www.dschmidt.com/images/mpgui...tchedBoard.JPG
http://www.dschmidt.com/images/mpguino/2nd/Front.JPG
http://www.dschmidt.com/images/mpguino/2nd/Side.JPG
http://www.dschmidt.com/images/mpguino/2nd/Back.JPG

Ends up I'm going to make a bunch of these due to requests on GMF. Board is out being fab'd, should have it next week.

Pretty much the same board as shown in my posts above but with added traces to feed the 2 unused analog inputs on the ATMega for those that want to add other features. Also added in a 6 pin ICSP header for programming.

Only comes with the switches shown but I do have solder pads for adding external switches (you can cut the bats off the existing switches if you don't want to use them).

Will be assembled - I laid out the board for my ease of assembly and cost so I'm using SMT parts, some thru hole where the parts are cheaper.

Stay tuned (I don't frequent this page that often)
(oh, and I need to update my signature - my metro is up to 411,000 miles on the original engine).

Let me know when you get them ready as I would like to buy one.

Shouldn't be longer than 2 weeks from now as the boards should be in my hands this time next week.

2nd.

Boards came today. Stuffing them now.

They're ready.

http://www.dschmidt.com/MPGuinoJBD.html

Documentation is here
http://www.dschmidt.com/pdf/MPGuino_JBD.pdf

In stock and ready to ship (first shipments went out today)
http://dschmidt.com/images/mpguino/Rear-2.jpg
http://dschmidt.com/images/mpguino/TBlocks.jpg
http://dschmidt.com/images/mpguino/Batches-2.jpg

Saweet!

User's over at GMF are starting to receive their units.
MPGuino, JBD layout

Ordered mine, can't wait for it to get here. I had built one myself but it was a wiring craphouse compared to this :)

Your order is shipping today, thanks!

Ordered for use on my CBR250R. Thanks.

Thanks. Will process tonight and email you a delivery confirmation number. Will go out in tomorrow's mail.

So whats your total cost for each of these? Like what does it cost you to make?

It's a secret :)


Seriously though, total COGS (cost of goods = materials only) is just under $20, including shipping box.

I'm hand building each and every one of these (which is why many of the parts are SMT - easier for me)

It's hard to believe he's selling them so cheap I know.

So cool! I thought I was going to have to break out the soldering iron. Ordered one, can't wait to get it and really compete with my wife's prius!

Shipping out tomorrow!

Hi I am from New Delhi India
Can you shio it to New Delhi if yes can you please tell me the price along with freight to New Delhi
Thanx
Sunny

Hi Jellybean Driver I am from New Delhi India
Can you ship it to New Delhi if yes can you please tell me the price along with freight to New Delhi & what will be the mode of Payment
Thanx
Sunny

Got it. It looks great. Does the three pin regulator need to be bolted and pasted down? Mine is loose.

No. The LCD I'm using, the backlighting takes about 5mA so the total current draw of this whole MPGuino with the display on and at the brightest setting is <30mA. That regulator is not going to get warm at all - no need to bolt it down.

For those buying the bare MPGuino board from me to mount up their own display, I do bolt it down since I do not know what current draw LCD display backlighting they are going to use. (see pictures on my website)

Yes, I will PM you a price.

Thanx jellybean

mode of payment please
need it urgently
thanx
sunny

Sent in a PM already. I'll resend

Is the screen of the display 100% weather proof or should I seal an additional lens over it for use on my motorcycle.