Proof reading Schematics, Anyone?

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Nutsy
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Proof reading Schematics, Anyone?

Post by Nutsy » Fri Sep 02, 2016 1:04 pm

Hi I know its a lot to ask as it takes time... But I'm some what at the stage in my project to start making the more or less final circuit diagrams and PCB layout designs.

As I'm far from an expert I could do with some proof reading and suggestions for some resistor/cap/stuff values... And also suggestions weather I need certain parts or not.

As you can imagine its not an insanely complex diagram but but if anyone can put in a little time to take a look for me, I would really appreciate it.

The attachment is just a indicator of how complex it is... Once I finish cleaning it up and putting in the values as I've worked them out ill upload a higher res, or even the eagle file.

Look at post below \:)
Last edited by Nutsy on Fri Sep 02, 2016 4:39 pm, edited 1 time in total.

Nutsy
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Re: Proof reading Schematics, Anyone?

Post by Nutsy » Fri Sep 02, 2016 4:38 pm

I might as well just post the full thing and hope some one can chip in :)

I have a few key areas I want anyone to look at as well as the whole thing...

The 1000 uf caps on the led arrays, are they really needed? The adrafruit neo pixel guide suggests they are, but I just got my caps in the post today and theyre pretty big. Are there any smaller ones i could use? Also i got electrolytic ones, Im not sure if that was right... Can anyone confirm?

Bellow the bike mains in i have my RPM signal in and opto isolator... The current assumption until i get an oscilloscope on the line is that the RPM signal will be the bikes voltage pulsing... IE 12-15v pulses to trigger the spark plug.

R2 i have no idea what to use there as the forward voltage is meant to be 1.2ish v, does it want to be a 630ohm resistor line the other short usage lines like right and left indicator? (found on the right side of the maple mini)

Are these 630 ohm resistors going to be fine reading off the raw bike voltage? Or will they go pop?

Ive also been using 7805 voltage regulators for some of the longer usage lines in like the running lights and highbeam, again the package is quite large and i rather have something smaller. But am i using them correctly? And do i need to worry about heat?

Please if you guys can have a look over
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racemaniac
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Re: Proof reading Schematics, Anyone?

Post by racemaniac » Fri Sep 02, 2016 5:22 pm

small suggestion: you could wire the dataline of the neopixels to an SPI MOSI line, if at some point you'd want to use SPI DMA for driving it, then you could :) (and then leave the other pins of that spi port free so it doesn't interfere with other things).
I've been experimenting with using spi dma to drive the neopixels, and it works really well :) (got the idea when i heard that's how they do it with the raspberry pi :) ).

Nutsy
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Re: Proof reading Schematics, Anyone?

Post by Nutsy » Fri Sep 02, 2016 5:40 pm

Im not really planning on using SPI at this stage... Maybe when I do the anti theft GPS tracker version.... but at the moment im not planning on it. Are there any performance bennifits to using mosi miso? Ive noticed its a little slower talking to neopixels with the fast led library on the maple than it is on the arduino...

But I do need to keep the AINs for the voltage testers...

racemaniac
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Re: Proof reading Schematics, Anyone?

Post by racemaniac » Fri Sep 02, 2016 5:53 pm

Nutsy wrote:Im not really planning on using SPI at this stage... Maybe when I do the anti theft GPS tracker version.... but at the moment im not planning on it. Are there any performance bennifits to using mosi miso? Ive noticed its a little slower talking to neopixels with the fast led library on the maple than it is on the arduino...

But I do need to keep the AINs for the voltage testers...
I'm not sure how you're currently implementing the protocol, but being able to just dump a "frame" of data in memory & then having DMA push it out for you while the cpu can do other stuff is pretty convenient :).
But if that's not your goal, indeed don't bother :).

Nutsy
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Re: Proof reading Schematics, Anyone?

Post by Nutsy » Sat Sep 03, 2016 9:48 am

Please some one take a look, i really want to know if the setup is alright before i set fire to my breadboard :D

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ahull
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Re: Proof reading Schematics, Anyone?

Post by ahull » Sat Sep 03, 2016 1:04 pm

I took a "quick look" and it was pretty quick. Only things I thought worthy of comment.

The opto-isolator resistor values.

R3 - You can probably get away with a higher value for R3, 1k 4k7 or even 10k would probably work.
R2 - Pick a value based on driving the LED at around half its maximum rated current based on whatever the voltage coming from the RPM signal is.
Typically with an opt-isolator, since the receiver is pretty close to the transmitter, you don't need to drive the transmitter LED very hard.
Either check the datasheet for the PC817 for the LED voltage, or estimate using http://ledcalc.com/ and assuming a red LED (typically the IR led in an opto-isolator is pretty close in spec. to a red LED, so good enough for the purposes of our exercise). If you are unsure what the peak voltage of the RPM signal is, stick an oscilloscope on it.

Failing that, if you don't have access to a 'scope, put a 100k variable resistor (POT) in between the signal and ground, then slowly adjust till you get a suitable signal out of the wiper to flash a standard red LED with a 100 ohm resistor in series. Start with the wiper at the grounded end of the pot and increase the voltage gently. The POT acts as a voltage divider, and the 100 ohm resistor will give the LED a sporting chance of surviving even if you are a little over enthusiastic twiddling the POT.

Blowing up red LEDs is less painful than blowing up opt-isoplators soldered to PCBs. :D

Once you are happy with those values then substitute the opto-isolator and see if the smoke safely remains within the little black blob. ;)

If, however you *know* the peak voltage of the RPM signal is say 12V then you can simply use a single resistor..
Here is an example...
http://www.sunrom.com/p/pc817-low-volta ... ptocoupler

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- Andy Hull -

Nutsy
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Re: Proof reading Schematics, Anyone?

Post by Nutsy » Sat Sep 03, 2016 2:33 pm

Heh thanks Andy great advice :D using that i've adjusted a few resistors. So R2 will be 680ohms as well the r14 and 12 from the indicators...
Ive got some 4.7k resistors already so ill use them on R3 and the other resistors in that type of circuit.

If 680 is a good safe bet and works well i will probably remove all the 7805s from my inputs and replace with an opto and resistor setup. Should save space, and hopefully some heat maybe?

I have a scope on the way, its a cheap Chinese DIY one im sure you all seen them... A bit noisy limited range but would do the job for me... Oh the life of the poorper, cheap chinese bike, cheap chinese arduinos and maples made with cheap chinese parts all tested on a cheap chinese scope :D What could go wrong :D

I may not like their political system but thank god for the chinese... Or i wouldn't have been able to do any of this :P

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ahull
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Re: Proof reading Schematics, Anyone?

Post by ahull » Sat Sep 03, 2016 8:10 pm

Nutsy wrote:Heh thanks Andy great advice :D using that i've adjusted a few resistors. So R2 will be 680ohms as well the r14 and 12 from the indicators...
Ive got some 4.7k resistors already so ill use them on R3 and the other resistors in that type of circuit.
680 Ohms sounds like a good compromise, 1k would probably work just as well, and might give you a little more of a safety margin, experiment and see.
If 680 is a good safe bet and works well i will probably remove all the 7805s from my inputs and replace with an opto and resistor setup. Should save space, and hopefully some heat maybe?
Opto-isolators are a better bet anyway, since you don't need to worry too much about having a common ground, you can in theory completely isolate your circuitry from the bike, and it will still work. They also provide a measure of high voltage surge protection that the 7805 wont. This is why data logging test equipment like multimeters will have opto-isolated serial ports. See here for how to hack a serial port on to a cheap multimeter -> http://www.kerrywong.com/2016/03/19/hac ... ltimeters/ <- The opto-isolator in these provides safety isolation up to several kV.
I have a scope on the way, its a cheap Chinese DIY one im sure you all seen them... A bit noisy limited range but would do the job for me... Oh the life of the poorper, cheap chinese bike, cheap chinese arduinos and maples made with cheap chinese parts all tested on a cheap chinese scope :D What could go wrong :D

I may not like their political system but thank god for the chinese... Or i wouldn't have been able to do any of this :P
Having grown up with a combination of limited budgets, and Scottish ancestry, the habit of only spending money if you need to is pretty familiar territory. I do own a couple of CRT oscilloscopes, but they were both 2nd hand and were in need of repair when I bought them, so I picked them up for pennies. Fixing them was half the fun, but be aware that "real" oscilloscopes tend to have some pretty hazardous voltage inside.
These little scope kits are fine for low frequency work, a half way house between a multimeter and a "real" oscilloscope. You could also build a pig-o-scope from a "blue-pill" but you would need to make a front end for it to let you measure voltages >3v3
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Nutsy
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Re: Proof reading Schematics, Anyone?

Post by Nutsy » Sat Sep 03, 2016 8:32 pm

Lol fantastic :D I realise this DIY scope is off a STM as well, and I did wonder if it was possible to make a scope with one of the spare baites i have...

Ill still build this DIY one when it turns up but I might have a go at the project. And I noticed while skimming the forum threads of your that you may have got 2Mhz working :) That seems great :D

Umm this might sound really cheaky... But do you have a finished project I could look at and maybe kinda copy, to build?

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