PCB Layout

rxhul

Active member
hi everyone

I am using this pcb (image below) as a template but want some help understanding a few things:

basically, if there were only 4 outputs (3 leds and a buzzer) and two more inputs, how could I best transfer this template to a 14M2 Pic?

specific questions:
why is there no 22 k resistor in the download socket?
how come the download socket doesnt go to serial in/out respectively, which I believe is the last pin on the bottom and - my supervisor has told me to do this..
(ill send an image to explain if this isn,t clear - really sorry!)
finally, why is it okay for the track coming from the digital temperature sensor and PTM potential dividers to go to the pic from below the resistor - don’t potential dividers usually have their track coming from the middle, in between the two components?

Many thanks

23299
 
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rq3

Senior Member
It's impossible to answer your questions, since we don't know what the intent of the designer was. The circuit as shown certainly could use some improvement! An actual schematic that makes sense would be a good place to start, rather than a "schematified layout". I've been doing PCB design for half a century, and this makes my head hurt. I'm not even sure whether I'm looking at the top or bottom of the board. For example, without knowing what the transistor (?) is that's driving the buzzer(?) there's no way of knowing whether the pins are correct (E,B,C).
 

lbenson

Senior Member
You have 3 LEDs and what I assume is a buzzer driven off of the upper right 4 pins of the IC, so you could leave those and adjust everything else so that it uses the 14-pin 14M2 rather than an 18-pin whatever. This would occupy pins B.2-B.5.

Then you could shift your inputs down to use C.0-C.4. B.1 is also available if you need it.

You do need the download circuit--see manual 1.
 

rxhul

Active member
It's impossible to answer your questions, since we don't know what the intent of the designer was.
I believe that the circuit shown was the primary design of a moisture/temperature sensor but I'm not 100 percent sure so please don't take my word for it.

The circuit as shown certainly could use some improvement!
That's what I thought! Phew...The thing is, the final version of the circuit looks even more complicated because the designer has tried to minimise board space - but then again the mistakes are said to have been corrected tho I'm not sure.

I will attach an image of the final PCB design here in another post.

The transistor is powering the buzzer.

You have 3 LEDs and what I assume is a buzzer driven off of the upper right 4 pins of the IC,
That's right. Many thanks lbenson
The thing is, my circuit is getting quite convoluted because there are 5 inputs. On top of this, there was the confusion of where the download socket goes to. A lot of lines are getting crossed over.

(Thank you because Manual does clearly show that the download circuit must go to serial in out.)

I think it will be easiest if I attach a picture for you of what I mean with my PCB

Many many thanks to both for your responses.
 

rxhul

Active member
This is the final circuit design.
my thinking was if I understood the first circuit then I would understand the final one better which makes my head spin too!

again, it may be a mistake to confuse things by adding this 'template' in so I will send my circuit which is specific to my circumstances in a bit after I have made a few additions.

thank you
23301
 

rxhul

Active member
are the pins for 9V and 0V interchangeable? the diagram above seems to show pin 5 (0V) conect to the power supply and pin 14 (9V) connnected to ground
 

erco

Senior Member
Looks like a circuit from Genie. I just looked them up. Appears to a be a Picaxe knockoff? Only one seller here in the US, with ridiculous prices. No wonder I've never heard of them.
 

lbenson

Senior Member
You have to keep 9V away from the picaxe--about 5.5V is maximum. Depending on usage, 3-AA batteries (around 4.5V) makes for a good supply, especially for testing. Once you're pretty sure you have things so that there will be no shorts you can use a 5V phone charger. If you +really+ need 9V somewhere (why?), you will need to regulate it down to 5V. As was pointed out in another recent thread, "not much stuffing in a 9V battery".

Four outputs and 5 inputs should work perfectly on a 14M2.
 

rxhul

Active member
Many thanks guys for your patience - please find attached my PCB in several forms.

(BTW - yes erco, the circuit is based on GENIE Circuit

in answer to rq3's comment - this is a circuit which randomly turns on an LED and then the user hits the pressure pad above said Led the user can change modes by pressing the first PTm and the variable resistor alters the speed at which the training takes place.

if this circuit is now looked at in Context with the previous discussion..

what improvements would you recommend
are the connections using the bridging wires okay?
finally, all advice is much appreciated

cheers
rxhul 1573938767595.jpeg1573938989484.jpeg1573938767595.jpeg1573938989484.jpeg
 

lbenson

Senior Member
It appears to me that 5V out of the regulator is connected to 0V on the battery, and that 0V on the 14M2 is not connected to anything (unless there is supposed to be a link there at the lower right where it approaches the trace along the bottom).

Are wire links implied for the connections to C.1, C.2, and C.3? And elsewhere?
 

inglewoodpete

Senior Member
A couple of points. First, to answer your question in post #1 about the 'missing' 22k resistor. If you are using a download cable that provides +5 and 0v for its data output (like the AXE027), then the 22k resistor is not essential. However, some serial cables output RS232 levels (up to +-12v), which require the 22k current-limiting resistor to protect the PICAXE's input pin. PICs have small internal protection diodes built into their silicon to bypass voltages over- and under- the chip's supply voltage. The 22k resistor limits the current and prevents the protection diodes and input circuitry from turning to toast.

9 volt PP3/216 type batteries are a very inefficient and ultimately expensive way to power a 5 volt circuit. Since you appear to be designing a PICAXE circuit board, consider using a 3 x AA battery enclosure (=4.5v) for the power source.
 

rxhul

Active member
It appears to me that 5V out of the regulator is connected to 0V on the battery, and that 0V on the 14M2 is not connected to anything (unless there is supposed to be a link there at the lower right where it approaches the trace along the bottom).
Many thanks lbenson

yes, the 0V on the 14M2 is connected to the rail by coming across the resistors and jumping over the transistor rail. - wasnt sure whether I had done it correctly though!

Are wire links implied for the connections to C.1, C.2, and C.3? And elsewhere?
The connections for C1 C2 C3 and C5 and 0V - i was trying to avoid making the tracks cross.

A couple of points. First, to answer your question in post #1 about the 'missing' 22k resistor. If you are using a download cable that provides +5 and 0v for its data output (like the AXE027), then the 22k resistor is not essential. However, some serial cables output RS232 levels (up to +-12v), which require the 22k current-limiting resistor to protect the PICAXE's input pin. PICs have small internal protection diodes built into their silicon to bypass voltages over- and under- the chip's supply voltage. The 22k resistor limits the current and prevents the protection diodes and input circuitry from turning to toast.

9 volt PP3/216 type batteries are a very inefficient and ultimately expensive way to power a 5 volt circuit. Since you appear to be designing a PICAXE circuit board, consider using a 3 x AA battery enclosure (=4.5v) for the power source.
really appreciate your help inglewoodpete!
that clarifies many things. So I still need the 22k resistor in mine?

i will think about changing the battery power source - it would be foolish not to!

23309
this is the whole image of the way the designer of the template made his circuit better and better.
a big appeal to all the geniuses out there including the ones that have helped me so far!! :

could you please help me understand some of the more intricate parts here and thus explain how I could emulate this confusing example to decrease my board size. I tried having a look at where the designer has moved the pins but by the time I get to the 3rd iteration I’m completely lost
.

many thanks everyone for all advice
really really appreciate it.
 

rxhul

Active member
If you want, to make it easier, you can download the image/take a screenshot and then zoom in to get a better look at the PCB and the writing.
 

inglewoodpete

Senior Member
really appreciate your help inglewoodpete!
that clarifies many things. So I still need the 22k resistor in mine?
I don't have enough information to tell whether the 22k resistor is needed or not. If you are not certain that any programming lead that would be used to program your board will output only TTL levels, then it would be safest to include the 22k resistor. What programming lead are you planning to use?
 

rq3

Senior Member
If you want, to make it easier, you can download the image/take a screenshot and then zoom in to get a better look at the PCB and the writing.
I suspect that starting from square one would be easier than trying to salvage the layout that you have. Even the "final" design has a lot of omissions and errors. The layout is pretty straightforward, and the process generally involves starting with a complete (and I mean complete) schematic and parts list.

Then break the design into functional blocks:
1) A power source. In your case a +5 volt supply, either batteries or a wall wart.
1a) Lots of bypass capacitors for the supply
1b) Heavy power and ground traces. If you are having a PC board fabricated, use power and ground planes.
They don't cost any more, and make the layout MUCH easier as you can avoid all the jumpers and crossovers
2) A PICAXE, which you would plunk down in the center of the design, and work out from
2a) The Picaxe programming circuit, per the manual, with a 3 pin connector to access it
3) The Inputs
3a) Switches, sensors, etc., from power or ground (as appropriate) to the central Picaxe
4) The Outputs
4a) Switches, sensors, LEDs, Buzzers, transistors, etc., from the Picaxe to the output device with current limiting resistors as needed

This is just a 30,000 foot view of the layout process, but I think the original designer got lost in the details because he never had them! That pesky transistor is the best example. He never did decide where base, emitter, and collector were (or drain, source, and gate), and even in the final design at least one pin is left hanging in space and never makes it to the buzzer (or maybe a long jumper wire was intended).

One of the neat things about doing a layout for a microprocessor is that the pins are programmable. Many can be either inputs OR outputs (or both), so a lot of jumpers and trace contortions can be avoided by keeping that in mind.

If you could draw a complete and correct schematic that we could all critique, I'd be happy to do a layout that we could also all critique. Right now we're all trying to fix a pretty badly botched previous effort.
 

rxhul

Active member
I don't have enough information to tell whether the 22k resistor is needed or not. If you are not certain that any programming lead that would be used to program your board will output only TTL levels, then it would be safest to include the 22k resistor. What programming lead are you planning to use?
I'm not sure which programming lead I am using, but since i've been told to use a 22k resitor I will just use one just to make sure.

That pesky transistor is the best example. He never did decide where base, emitter, and collector were (or drain, source, and gate), and even in the final design at least one pin is left hanging in space and never makes it to the buzzer (or maybe a long jumper wire was intended).

...

If you could draw a complete and correct schematic that we could all critique, I'd be happy to do a layout that we could also all critique. Right now we're all trying to fix a pretty badly botched previous effort.
Firstly, I am very sorry rq3 - you seem like an extremely wise and experienced member (just like everyone else!)
I understand that I have confused things.
I just added that 'botched example' to give an idea at what we may be dealing with in terms of how the board size is reduced.

If we forget that whole circuit...

Please could you have a look at the PCB i posted on this thread at 9:22 last night?
This is my circuit
and this is one I want everyone to critique (really sorry for this confusion).

In terms of the schematic, I thought that was the black thing which I posted (also at 9:22)

Possibly you could show me what you mean with a drawing.

In terms of parts list:

Battery holder
Switch
Voltage Regulator (With capactiors)
Indicator LED (green)
PTM - to switch between modes
Variable resistor - to change the speed in 2 of the modes of how fast the LEDs comes on
3 PTMs - pressure pads which the user hits with their sword (this is a reaction timer)
3 LEDs, acting as the stimulus/indicator and are located beneath the transparent pressure pad
Transistor, + Buzzer, - makes a noise each time the correct pad is hit.
Obviously, 14M2

(Thanks particularly rq3 for giving some order to my train of thought!)

I think that's everything and would like to thank everyone for their patience with me as I am still learning but trying my best!
 

rxhul

Active member
1a) Lots of bypass capacitors for the supply
1b) Heavy power and ground traces. If you are having a PC board fabricated, use power and ground planes.
They don't cost any more, and make the layout MUCH easier as you can avoid all the jumpers and crossovers
2) A PICAXE, which you would plunk down in the center of the design, and work out from
2a) The Picaxe programming circuit, per the manual, with a 3 pin connector to access it
I don't really understand this bit, but once we've sorted out the confusion re the schematic we can then come to this, I feel.
 

hippy

Technical Support
Staff member
I'd have put that pot across 0V/+V ...
POT.gif
And you don't need to break the two horizontal lines below it if you run the pot's 0V to the bottom of the 10K to the right.
 

lbenson

Senior Member
A possibility is to start with a design like this:
23313
All the 14M2 pins are brought out in a single row. Programming circuit is included, and a 2-pin connector for power. You could make your design a separate board that this plugged into, or could modify the eagle cad files attached to make a single board. Boards can be very inexpensively ordered from jlcpcb.com. With slow boat shipping, five copies of the 14sip2.pcb file attached below would be only about $10US. 10 copies is a dollar more.

The eagle cad files attached below have .zip added to them so that they can be posted on the forum. To use with the eagle program or to send directly to jlcpcb, simply rename without the .zip extension.
 

Attachments

rxhul

Active member
I'd have put that pot across 0V/+V ...
View attachment 23314
And you don't need to break the two horizontal lines below it if you run the pot's 0V to the bottom of the 10K to the right.
Hi hippy - I can't see your full image, only a part of it.

Also, this may be a stupid question but, what is a "pot" what do you mean in your last sentence.

Reallly sorry!
 

rxhul

Active member
A possibility is to start with a design like this:
View attachment 23313
All the 14M2 pins are brought out in a single row. Programming circuit is included, and a 2-pin connector for power. You could make your design a separate board that this plugged into, or could modify the eagle cad files attached to make a single board. Boards can be very inexpensively ordered from jlcpcb.com. With slow boat shipping, five copies of the 14sip2.pcb file attached below would be only about $10US. 10 copies is a dollar more.

The eagle cad files attached below have .zip added to them so that they can be posted on the forum. To use with the eagle program or to send directly to jlcpcb, simply rename without the .zip extension.
Hi lbenson,

Unforunately, we have to keep our circuit on GENIE Circuit Wizard - this would be too complicated for the time that I have. I'm bewildered. Sorry to waste your time and efforts.

Alternatively, if you could offer any improvements to reduce my PCB, as in the 'template' above, that would be great!

Many thanks.
 

rxhul

Active member
Hi hippy - I can't see your full image, only a part of it.

Also, this may be a stupid question but, what is a "pot" what do you mean in your last sentence.

Reallly sorry!
i was being quite dumb - the pot is a potentiometer.

i found on the internet that you only connect one leg out of the bottom two on the pot, and the third leg you don't connect at all..

But otherwise that looks quite clever!

Thanks!
 

AllyCat

Senior Member
Hi,

Personally I'd go right back to square one and ask Why you are designing this Circuit Board. Is it for an "Educational" purpose (either formal or self-taught), or because you plan to make many units, or to look "professional", or because you think it is the "right" thing to do? Of course the first rule for an educational environment is to keep the tutor happy. :)

In my professional life I often designed PCBs and enjoyed the "challenge" of designing them as small as possible (which was also worthwhile if thousands were to be made), but nowadays I normally just build on "Veroboard" (stripboard) - it's a much quicker way to discover your design mistakes ! Take a look at "Pebble" in the downloads section; IMHO it's an excellent way to start, even if you ultimately plan to go to PCB: Two of the most fundamental concepts of (initial) PCB design are that tracks on one side of the PCB go North-South, with East-West on the other side, and you can use components (particularly resistors and diodes) to "bridge" (jump over) tracks (to avoid using a wire link). I'm afraid I have to disagree that an earth plane is always a "good idea" - they can be a nightmare to fix if you design in an incorrect connection, and even soldering component legs can be horrible if "thermal relief" pads have been omitted.

To answer a couple of your questions: No, what you have shown is not really a "schematic diagram" - they use pure electronic "symbols" (which often bear little resemblance to their physical shape) and as far as practical adhere to the "norm" of signals flowing from left to right (i.e. inputs on the left and outputs on the right), with the supply rail at the top and ground (rail) at the bottom. Of course that's not entirely possible (for example the programming socket is both an input and an output), but the nearer you can get, the easier it will be for others to find any design mistakes. ;)

Finally, the "22k", (which doesn't actually need to be 22k, but could be anything between about 1k and 100k) serves (at least) two purposes, so I would always include it: As already said, it limits the input current to a safe level, if the input voltage "strays" outside the supply rails, either due to a connection mistake, or just static electricity. Secondly, it helps to pull the programming pin down to ground (in association with the "10k" in the standard circuit) which is absolutely essential for correct operation of the PICaxe.

Cheers, Alan.

PS: No, a "Potentiometer" does need three connections. If you connect only two pins of a "Pot", then it becomes a "Variable Resistance". ;)
 

rxhul

Active member
Thank you Alan - The project is for educational purposes but for an internal project. So yes, the tutor must be kept happy...!

The alternatives do look much better but unfortunately, I have to follow some things that my tutor has told me...i.e use GENIE circuit wizard.

I still don't get how I would draw a schematic for my circuit. Would you be able to show me what the schematic (for my circuit preferably!) would look like please??

Finally, what is the difference between the "potentiometer" and a "varible resistor" - would they serve the same function?
I just want to change the speed so surely i just need a VR?

Many thanks.
 

rq3

Senior Member
Hi lbenson,

Unforunately, we have to keep our circuit on GENIE Circuit Wizard - this would be too complicated for the time that I have. I'm bewildered. Sorry to waste your time and efforts.

Alternatively, if you could offer any improvements to reduce my PCB, as in the 'template' above, that would be great!

Many thanks.
Here's a quick and dirty schematic just to get you startedExample.jpg. You'll need to decide on your battery, and whether or not it needs an ON-OFF switch. The input switches make use of the Picaxe internal pull-up resistors (if applicable, you'll have to check), so each switch doesn't need a resistor. The two capacitors are the by-pass caps critical to any layout, and they should be as close as physically possible to the Picaxe.

If running off 4.5 volt batteries, or even a 3.6 volt lithium coin cell, you could safely omit the three LED resistors. And you'll need to decide how you want to connect the three programming pins to the outside world (SERIN, SEROUT, GROUND).
The standard PICAXE programming cable has a three contact stereo plug on the end, and most folks use the mating socket.
 

lbenson

Senior Member
Finally, what is the difference between the "potentiometer" and a "varible resistor" - would they serve the same function?
A variable resistor varies the amount of current which can pass through the resistor--as, for instance, with fixed resistors, an LED with 330 ohm resistance in series will be brighter than the same LED with 1K resistor, because more current can pass through the 330R. A potentiometer is a voltage divider (in addition to providing current-limiting).

A fixed resistor-divider example might be 5V connected to a 1k resistor connected to another 1k resistor connected to 0V. If you put your voltmeter on the connection between the two resistors, it will read 2.5V--the voltage is divided in half because both the upper and lower resistors is the sam. With a potentiometer instead of the 2 resistors, the resistance between 5V and the center point, and between that point and 0V both change, so you may get a range between 5V and 0V when you adjust the pot.
 

lbenson

Senior Member
If running off 4.5 volt batteries, or even a 3.6 volt lithium coin cell, you could safely omit the three LED resistors.
I don't think that's the case--the picaxe does not itself provide current limiting, and unlimited 4.5V or 3.6V could burn out a picaxe pin, although a picaxe pin can reportedly sink more current than it can source (I have not intentionally tested to destruction).
 

rxhul

Active member
A variable resistor varies the amount of current which can pass through the resistor--as, for instance, with fixed resistors, an LED with 330 ohm resistance in series will be brighter than the same LED with 1K resistor, because more current can pass through the 330R. A potentiometer is a voltage divider (in addition to providing current-limiting).

A fixed resistor-divider example might be 5V connected to a 1k resistor connected to another 1k resistor connected to 0V. If you put your voltmeter on the connection between the two resistors, it will read 2.5V--the voltage is divided in half because both the upper and lower resistors is the sam. With a potentiometer instead of the 2 resistors, the resistance between 5V and the center point, and between that point and 0V both change, so you may get a range between 5V and 0V when you adjust the pot.
so, as far as I can understand, i should use a 'pot' for my speed altering system
 

rxhul

Active member
Here's a quick and dirty schematic just to get you startedView attachment 23317. You'll need to decide on your battery, and whether or not it needs an ON-OFF switch. The input switches make use of the Picaxe internal pull-up resistors (if applicable, you'll have to check), so each switch doesn't need a resistor. The two capacitors are the by-pass caps critical to any layout, and they should be as close as physically possible to the Picaxe.

If running off 4.5 volt batteries, or even a 3.6 volt lithium coin cell, you could safely omit the three LED resistors. And you'll need to decide how you want to connect the three programming pins to the outside world (SERIN, SEROUT, GROUND).
The standard PICAXE programming cable has a three contact stereo plug on the end, and most folks use the mating socket.
My sincere apologies, but rq3 you have lost me..
would it be possible for you to critique the original circuit ?
 

lbenson

Senior Member
would it be possible for you to critique the original circuit ?
You still have 5V from the regulator connected to 0V on the battery--a dead short.
Do i not need to connect the pot in a potential divider with a 1k resistor?
The pot in the circuit is wired as a variable resistor--the 1K resistor which connects the wiper (the top pin in the diagram) to 5V makes the combination of 1K + pot a voltage divider. I'm not sure what range of ADC readings you are expecting to get on pin C.1, but C.1 is not an ADC pin at all (see "At a Glance" in Manual 1)--you need to connect to another pin. This is an atypical use of a pot, but it does protect against a coding mistake which would make the pin it is connected to a LOW output, which would essentially be a dead short to 5V. This would not be an issue if the pin were never made an output pin. See Manual 3 for a more typical wiring of a pot, with 5V, 0V, and wiper all connected.
 
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rq3

Senior Member
I don't think that's the case--the picaxe does not itself provide current limiting, and unlimited 4.5V or 3.6V could burn out a picaxe pin, although a picaxe pin can reportedly sink more current than it can source (I have not intentionally tested to destruction).
Ibenson, for the purposes of THIS discussion, I should never have even suggested it. My apologies for adding to the confusion, rather than the clarification. In reality, the pins ARE current limited, as any MOSFET is (to a point). The P channels (output high) have about 90 ohms of intrinsic silicon impedance, while the N channels (output low) have about 30.

With the right LED, and the right supply voltage, and the right environmental conditions, a PIC can safely drive an LED directly and stay within its current and temperature limits.

But. This was not the place to bring it up, and I thank you for flagging it. Note that I did include LED resistors on my quick and dirty schematic ;-)

I'm guilty of providing TMI for Rxhul.
 

AllyCat

Senior Member
Hi,
I still don't get how I would draw a schematic for my circuit.

Finally, what is the difference between the "potentiometer" and a "varible resistor" - would they serve the same function?
I don't know "Genie Circuit Wizard", but any PCB design package should include a "Schematic Capture" facility. Basically, it needs a library of not very many symbols (Resistor, Diode, Capacitors, etc.) and normally the "difficult" part is later, when choosing the correct "footprints" (Through-hole, SMD, bridging distance, etc.). But here, we have a 14-pin footprint which can correspond with literally hundreds of different Symbols and maybe the PICaxe 14M2 is not supported?

However, the 14M2 has a very "logical" pin arrangement, so the symbol's Pin sequence can (IMHO should) be the same as the physical (Leg) sequence and the pin functions may be named with "Text" or even "net" (track) names, For a "schematic", I would always orientate Pin 1 (Vcc, supply) towards the "top", whether the long axis were N-S or E-W. There are many other "rules" that I try to apply to all my own schematic designs (in an attempt to reduce the effects of "Murphy's Law"), but I won't expound on them here. ;)

I was being a little pedantic about "Pots", but that's appropriate for an educational forum: A potentiometer is a "Variable Potential Divider", i.e. one terminal (end) is connected to a "signal" (maybe ac or dc) and the other end to "ground", or at least a lower potential. The "wiper" then reads off a voltage from across the track, determined by the resistances in the upper and lower sections. A typical application would take a PICaxe ADC input pin to the wiper and a READADC command could read any voltage between ground (0) and Vcc (e.g. 255).

If you connect only one end and the wiper, then you have a variable resistor, for example to use in series with a LED to control its brightness (i.e. controlling the V to I conversion according to Ohm's Law). But it's "good practice" to connect the "spare" end to the wiper: That makes it obvious that it's "intended" to be a VR (not a Pot.) and also if its track becomes "dirty", then the maximum resistance will be the value of the Pot and not "infinity" (which could be the difference between "still working" and "faulty").

Your "reference" design appears to use a 47k pot with a 1k pullup, which seems "weird" and is probably "wrong" because it will give a very strange "Voltage Law": Over the first 10% of its rotation the resistance will rise from zero to about 4k7 and the voltage at the junction from 0 up to over 4 volts (if a 5 volt rail). Then the remaining 90% rotation can only complete the journey up to the supply rail.

OT: Actually, at 3 volts (particularly with a coin cell), even the "short circuit" current through a PICaxe pin should be quite "safe" (it's documented in graphs towards the end of section 31 in the "base PIC" data sheets for the 08 to 20M2s). But personally I would never omit the LED series resistors (at least in a development design) because the resistors/links can be so useful to "jump" tracks (at least in single-sided PCBs) and can help with debugging, for example to measure current, or as convenient probe test points,, etc..

Cheers, Alan.
 

rq3

Senior Member
Rxhul, see if this layout makes sense to you, based on my previous schematic. I have not included the 9 volt battery, or the regulator, which make no sense in this application. Some components (buzzer, transistor, and pot) I based on your original footprints. This layout is reasonably tight, but no excessively so, and has no jumpers or crossovers. The traces should also be thicker, but that's up to you!

Between Ibenson and AlleyCat, I think you're in good hands here, though I think your supervisor on this project has thrown you into the deep end of the pool.
 

Attachments

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lbenson

Senior Member
Well, I had to attempt "test to destruction". I put a red LED directly on 2-AAs--pffft immediately, as expected. I didn't want to damage a 14M2, so I used an old 14M--so not exactly testing the hardware under consideration. With the picaxe wired as a current sink for the LED, I issued LOW C.1. After 5 minutes, all still bright and nothing warm. I switched to the picaxe wired as a current source. With HIGH C.1, the light was bright for 5 minutes--no problems. I switched to a 3-AAs--4.75 volts. The same two tests worked for 5 minutes each.

OK, then. Perhaps there would be a problem if you used too many LEDs which weren't current-limited, since there is an overall current limit for the picaxe. I'll continue to use 1K or greater resistors, since I find the LEDs are plenty bright for my purposes with those.

Who says you can't teach an old dog new tricks?
 
Having had a brief read through, the advice I was originally going to offer suddenly seems obsolete... However I'm going to give it anyway, in case someone comes back to this thread with a similar question at some point in the future.

If you are able, I would start by trying to create a "new" schematic from the layout/schematic you've been given. That allows you to gain an easy "overview" of each component and its interconnectivity.

I would (personally) download KiCAD, which is free (there are others available, personal preference here). On this, build a copy of the original schematic with all the connections etc. Once these have been drawn, go through the schematic, connection by connection, and replace each one with a label - name the labels something simple, like "butt1_+". Add the labels to both (or all, if multiple) ends of the connection. Use the built-in power flags (VCC / +5V / GND etc.) for those connections which are connected to a power or ground line.

Once you have replaced all the connections with labels, you can then easily select "blocks", consisting of a component and its labels, and move them into a more "user friendly" order. From there you can then rebuild the schematic to make it readable in whatever way you find best. I would keep the labels in place when you add a connection back in however...

To help you with putting the connections back in, you can import the schematic into KiCAD's PCB design suite, and use the Ratsnest - it shows you all the connections for a specific pad on a component, allowing you to easily rebuild all the connections in a more logical manner.

Once you have done all this, you can then use them as references when you go back into GENIE (or anything else if this comes up in the future), and rebuild your circuit from scratch in a more logical manner!
 

rxhul

Active member
Hi guys,

really appreciate everyone's help.

just a quick question - in the template above that had been causing confusion:

why does the designer use lacing holes which seem to go ”one above, one below” in stead of the 'normal' square configuration?

i hope I’m making sense..

cheers,
rahul
 

lbenson

Senior Member
I'm afraid I may not be alone in not understanding what you mean by "lacing holes". Can you point these out (perhaps by using MS Paint to draw circles or arrows).

A non-standard design tool was used to create this, so you may not get much feedback as to why things were laid out as they were.
 
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