Neatest PCB arrangement using schematic

rxhul

Active member
Hi guys,

Thank you for everyone who has made this possible.

I have spent far too long on this circuit, so I just want confirmation that this circuit below would work!
(And if there is anything huge, then a few critiques would be helpful).

From a prior discussion: lbenson, if you see this, then 'lacing holes' are highlighted in green below (just one example).

Many thanks,

Rahul
 

Attachments

lbenson

Senior Member
It's hard to tell. Components are unlabelled, links are implied. No schematic is provided to check the circuit against. At a minimum, the recommended 100nF decoupling capacitor isn't there as close to the PICAXE power pins as possible. The typical 10uF reservoir capacitor is absent (or near the regulator, not clearly labelled). The circuit might work, but there could be intermittant failures because of lack of the decoupling capacitor at the power pins.

Note: it is best to post images as jpgs, not as Word documents which could contain harmful scripts.

No idea what the "lacing holes" are intended to do.

It's a shame if your instructor or guide requires you to do this in a way which won't be helpful for any further work of this type.
 

rxhul

Active member
I'm unsure what a decoupling capacitor is..

Lacing holes are for the flying wires to connect offboard components. (PTMs and LEDs)

I know, but unfortunately, I must follow my instructor on some things..
 

AllyCat

Senior Member
Hi,

It seems to be too easy to hit the "like" button when I'm using my phone, but I do have to agree with all of lbenson's comments anyway. I had assumed that the "horrible" layout (cramped lower RH corner, too many links, spurious holes, unreadable component IDs, devious tracks to the programming socket,, etc.) was because the locations of components such as LEDs were fixed by "holes" in a pre-defined enclosure (box), but that seems not to be the case. BTW what is a PTM? Also, if that is a row of 4 push-buttons at the top, (of which one is not connected to the supply) then the (not shown) links to the PICaxe would be better specified as resistors, to avoid the risk of destroying the PICaxe if a button is pressed whilst an I/O pin is accidentally programmed to be Low.

The use of 9 volt "PP3" style batteries is highly discouraged for PICaxe applications, particularly now that you've identified the regulator as a 78L05. That regulator may dissipate (waste) about ten times more energy from the battery than the PICaxe uses ! Three AAA cells (or possibly even two) in a plastic holder (with the same connectors) will probably cost less, take little more space and run the application for up to 100 times longer!

If you have to use non-standard "tools", then you should at least post in an easily readable file format such as .PDF, .PNG, or .JPG, etc. Personally, I try to post everything "in line", including my 300 line programs ! As already said, there is so much information "missing" from the "schematic" (including what it is actually required to do) that it's very difficult to predict whether it might work, or not. But looking into my crystal ball: If the circle in the lower centre of the PCB is intended to be a "sounder", connected by a (not-shown) link to a transistor on its right, then that is unlikely to work, because both the "circle" and the "transistor" are connected to earth (i.e. there is no power supply).

YEScopy.png

Sorry! , Alan.
 

rxhul

Active member
Thanks Alan -

In terms of the bottom right hand corner - I was trying to making the layout as compact as possible. How could I make it better?

PTM is a push to make switch, same thing as a push button. Thanks for highlighting the fact that one of the push buttons isn't connected - i will fix that.

Same thing with the battery point. Many thanks!

When you say that I don't show the links, I assume you mean the holes that seem to jump across a copper pad? - I meant to indicate that these were bridging wires, so sorry if this wasn't clear.

The "circle" is indeed a buzzer, but can I just clarify...why does it need to be connected to the power supply, since the resistor, transistor combo is coming out of the output pin 8 on the picaxe. Is this not how it is meant to be...just like the LED outputs aren't connected to the 9V rail.

Thanks again and sorry for posting in the wrong format,

Rahul
 

hippy

Senior Member
The "circle" is indeed a buzzer, but can I just clarify...why does it need to be connected to the power supply, since the resistor, transistor combo is coming out of the output pin 8 on the picaxe. Is this not how it is meant to be
I believe the problem is that your circuit appears to be as follows -
Code:
----------------------------- +V

              .------.
              |     _|_
    ___    | /     |   |/|
---|___|---|<      |   | |
           | \     |___|\|
              |      |
--------------^------^------ 0V
Thus no way to actually pass current through the buzzer to activate it. What you need is ...
Code:
------------------------.--- +V
                       _|_
              .---.   |   |/|
              |   |   |   | |
    ___    | /    |   |___|\|
---|___|---|<     |     |
           | \    `-----'
              |
--------------^------------- 0V
 

rxhul

Active member
I believe the problem is that your circuit appears to be as follows -
Code:
----------------------------- +V

              .------.
              |     _|_
    ___    | /     |   |/|
---|___|---|<      |   | |
           | \     |___|\|
              |      |
--------------^------^------ 0V
Thus no way to actually pass current through the buzzer to activate it.
Many thanks hippy,

But won't there be a current coming from the output pin 8 through the transistor?

I'm just seeking further clarification BTW, because I see what you mean. I will change it!

Thanks both.
 

lbenson

Senior Member
But won't there be a current coming from the output pin 8 through the transistor?
But your transistor is configured as a "low side switch"--that means that the buzzer must be connected to power, and the transistor (when active) completes the buzzer circuit to 0V.

14M2 output pin B.1 "activates" the transistor, which means that it will conduct--but only if the thing that it is connected to is itself connected to power. (By the way, I don't know how loud you need it to be, but there are buzzers which will sound when only connected to a picaxe pin, without the need for a transistor.)
 
Last edited:

AllyCat

Senior Member
Hi,

Normally a PICaxe pin can't deliver enough current (nor maybe resist sufficient voltage) to drive a "buzzer", so the transistor is used as an "amplifier", which is a slight misnomer because it can only control or switch an external current, rather as a relay does. The sounder is actually the one component (in addition to the regulator) which might be connected directly to the 9 volt supply, to make it louder (because the transistor can safely resist that voltage), but that would depend on the buzzer's specification/rating. Also it's important that it is an active "buzzer" and not a (passive) "loudspeaker", which would need to be handled differently.

My comment about the layout was that the LEDs appear to overlap (they do seem quite large) and there are 8 components south the PICaxe and not much more than "white space" north of it. The white space might be a better location for the programming socket (nearer to Legs 2 and 13). If the LEDs are "off board" then they might be shown as a "header socket" to connect the wires, or perhaps look at how Rev Ed "anchor" the battery leads on most of their prototype boards.

As for the overall layout, it would normally be better to place the PICaxe nearer to the centre of the board, perhaps oriented N-S rather than E-W. There is considerable freedom in how the pins can be allocated, but it's sensible to start with the inputs (switches, etc.) on the LH Side (Legs 2 - 7), outputs on the RHS (Legs 8 - 13) and the programming socket at the top. There are advantages in taking push-switches to ground (rather than the supply) because there is less risk of accidentally damaging the PICaxe, and the internal "Weak Pullup" resistors can replace external ones. But it's probably worthwhile to include "current limiting" resistors in series with (all) the signal pins, and then they can be used also to "jump over" PCB tracks where required.

Cheers, Alan.
 
Top