Simple question I expect (Potential Dividers)

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SilentScreamer

Senior Member

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BeanieBots

Moderator
The two 0.1uF caps should be enough to prevent oscillation.
A quick glance looks like it's wired correctly.
You to eliminate the obvious first.
What is the unloaded voltage?
 
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Dippy

Moderator
Is your regulator correctly connected?

The Data Sheet shows:
1 = Vin
2 = Vout
3 = Gnd.

Your artwork shows Ground to the central pin I think.
(Which is a common pinout).
 
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SilentScreamer

Senior Member
The Connection Diagram above slightly above shows the middle pin to be ground.

Also what is unloaded voltage. The voltage from my battery is between 12V and 13V (its a lead acid battery). The output of the Voltage regulator is about 2.5 volts.

EDIT: Iv'e tried both ways round for soldering it in (on a new regulator) and had about 1V out i think.
 
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Dippy

Moderator
I posted above what the DATA SHEET (that you linked to) says.

The Data Sheet shows:
1 = Vin
2 = Vout
3 = Gnd.

Have another look. Never 'assume' anything.
 
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Dippy

Moderator
Ah, oops. Nil points. I was looking at the test circuit pinouts. Doh!

Can you double check with a regulator in a breadboard then, with your pinout as per circuit?

My only tip is always build up a circuit and test in sections. So when something causes something horrible to happen it helps zero in.

Edit: I notice ST have changed their Data Sheet and removed the pin numbers on their test circuits to reduce confusion for ninnies like me!
http://www.st.com/stonline/products/literature/ds/2148/l78s05c.pdf
 
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SilentScreamer

Senior Member
I'm sure my voltage regulator is the same on my PCB as my breadboard (I can't check again until monay as its still at school but I checked several times during my PCB development). It's just that it is giving out the incorrect voltage, almost regardless of the rest of the circuit it should give out the correct voltage shouldn't it? (unless there is a short but I'm 99% sure there isn't)
 
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eclectic

Moderator
@SilentS.

Only a possibility.
Have you got the board at home? If so,

1.Remove any large current-consuming outputs.
2.Remove the regulator chip.
3.Remove 28X / Firmware chips.
4.Get three cheap AA Zinc/Alkaline cells. NOT NiMH/NiCad.
5.Bodge some connectors to Gnd and the regulator OUT pad connection.

Do some DMM measurements at the Picaxe V+ and Gnd connectors.


Then PERHAPS, ever so carefully, do as Dippy suggested.
Start to rebuild.

Added. Bugger! Just noticed your post above!
 
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SilentScreamer

Senior Member
Is what I said in my above post true that the componets after the voltage regulator shouldn't affect its function or is there something I've overlooked?

Also I do have my PCB at home (my breadboard rarely survives the walk between school and home so it lives at school) as well as most tools and a reasonably good multimeter.
 
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holmedwa04

Member
Sorry to mention this if it has already been mentioned... but what about a voltage regulator? 5V would do? Would it not. And generally speaking you need about 7+ volts for the regulator to work correctly so... it will only provide about 4.5V anyway if you are running it on 6V?

Sorry to hijack this thread, I am requiring 5V for a receiver module and then 6V for a PICAXE 28X1, will this operate on 5V? because then I can use a plug in wall transformer at 9V and a voltage reg on both circuits?
 
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Dippy

Moderator
He's GOT a voltage regulator.
But he has a problem which means something odd is happening.
If its not a duff regulator (or other component) then its a cockup on the PCB.

DON'T stick 6V on a PICAXE!
Read the Manual. PICAXEs are very, very happy at 5V.
If possible power BOTH things off a single 5V reg.
If there are noise issues then use a separate 5V regulator for each with a commoned ground, but in most cases a single regulator is fine. Even noise probs can be got rid of with a bit of care.
Just check the device specs and (unlike me tonight) read the Data Sheet ;)
 
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SilentScreamer

Senior Member
holmedwa04 said:
Sorry to mention this if it has already been mentioned... but what about a voltage regulator? 5V would do? Would it not. And generally speaking you need about 7+ volts for the regulator to work correctly so... it will only provide about 4.5V anyway if you are running it on 6V?

Sorry to hijack this thread, I am requiring 5V for a receiver module and then 6V for a PICAXE 28X1, will this operate on 5V? because then I can use a plug in wall transformer at 9V and a voltage reg on both circuits?
Click to expand...
That and i'm running on 12V minimun input is 6.2 maximum is 35 so im well inside even if you wanted to run on 6V im sure low drop out (i think thats what they were called) ones exsit.
 
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holmedwa04

Member
Dippy said:
He's GOT a voltage regulator.
But he has a problem which means something odd is happening.
If its not a duff regulator (or other component) then its a cockup on the PCB.

DON'T stick 6V on a PICAXE!
Read the Manual. PICAXEs are very, very happy at 5V.
If possible power BOTH things off a single 5V reg.
If there are noise issues then use a separate 5V regulator for each with a commoned ground, but in most cases a single regulator is fine. Even noise probs can be got rid of with a bit of care.
Just check the device specs and (unlike me tonight) read the Data Sheet ;)
Click to expand...
I got the PCB foil for the picaxe 28X1 from the main website, and it says 6V, which is higher than the standard 4.5. I am using 6V at the moment without any noticeable problems/heating effects. But would like to run off 5V if I can.

As quoted from datasheet...

"The primary power supply (V1+) for the interface is a 6V or 4.5V DC"
 
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eclectic

Moderator
re post #55
SilentScreamer said:
Is what I said in my above post true that the componets after the voltage regulator shouldn't affect its function or is there something I've overlooked?

Also I do have my PCB at home (my breadboard rarely survives the walk between school and home so it lives at school) as well as most tools and a reasonably good multimeter.
Click to expand...
Have you tried the steps outlined in post #54?
Or am I answering a different question?

e
 
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SilentScreamer

Senior Member
eclectic said:
re post #55


Have you tried the steps outlined in post #54?
Or am I answering a different question?

e
Click to expand...
I will do either later tonight or tomorrow and post the results.

holmedwa04 said:
I got the PCB foil for the picaxe 28X1 from the main website, and it says 6V, which is higher than the standard 4.5. I am using 6V at the moment without any noticeable problems/heating effects. But would like to run off 5V if I can.

As quoted from datasheet...

"The primary power supply (V1+) for the interface is a 6V or 4.5V DC"
Click to expand...
The 6V is probably reduced though something because the absolute maximum is 5.5V or there abouts if i remeber rightly.
 
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Dippy

Moderator
An important digression.

I've just been looking at the 28-pin Project Board Data Sheet axe020.pdf available right this moment from the Website an has been around for years.
I assume that is the document being referenced by holmedwa04?

Is this a typo?

And yes, it does say:
"The primary power supply (V1+) for the interface is a 6V or 4.5V DC. This is connected via the battery connector. DO NOT use a 9V PP3 battery, as the interface does not include a voltage regulator."

Note the "6V". Subsequent schematics also show 6V.

Whilst this is within a PIC "Absolute Maximum Ratings" it is beyond the recommended voltage range for the PIC (typically 5.5V for 16Fs). From the circuit schematic I cannot see any voltage limiting.

Running beyond 5.5V will mean that the PIC functions wil be running beyond spec and may affect some operations (e.g. frequency and logic levels).

Surely this should be changed to ".. for the interface is a 4.5V or 5V DC" in that document?
[i.e. all mentions of 6V to be changed to 5V]
People have obviously proven that it will work at 6V, but this is beyond Microchip's recommendation and also can confuse Users (and me) as to the PICAXE 'recommended' voltage supply,

Obviously, every Newbie will have read "Getting Started" Manual 1 page 5 ("At a Glance") where it says:-
"....4.5V or 5V DC is recommended. Do not use 6V, 7.2V or 9V"

Note the "Do not use 6V...."

I bit of consistency is required here perhaps.....?
A) It's not right.
B) It confuses and 'sends the wrong mssage'.
 
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westaust55

Moderator
more on "important digression"

This situation is not limited to the AXE020. I have spotted many such inconsistencies in the PICAXE documentation in the past while referencing datasheets to answer questions.

An incomplete list from what I have seen in the past includes:

CHI008 datasheet page 2 states:
DO NOT USE A 9V PP3 BATTERY WITH THIS PRODUCT.
ONLY USE THE 4.5V or 6V (AA CELLs) BATTERY BOX SUPPLIED.
Click to expand...
CHI030 datasheet the schematic at bottom of page2 indicates “G” and “6V” for the PICAXE suppy

CHI035 datasheet the schematic at bottom of page2 indicates “G” and “6V” for the PICAXE suppy

CHI040 datasheet page 2 states:
Insert four AA batteries (not supplied) into the battery pack and then connect
to the battery clip.
DO NOT USE A 9V PP3 BATTERY WITH THIS PRODUCT.
ONLY USE A 6V (4xAA CELL) BATTERY BOX.
Click to expand...
The schematics at top of pages 3 and 4 also show 6V as the supply voltage.


Then there is page 7 of the PICAXE-08M RUDOLF PROJECT
 
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Dippy

Moderator
Mmm... well it looks like someone should spend a morning 'harmonising' the information.

It has to be said there's some handy info for Newbies in the Rudolph Data Sheet.
I notice they witter on about (up to) 6V for the micro but sensibly use a 3xAA in the kit.

I think hippy should do a Risk Analysis on this :)

A morning's editing could sort those aspects of the Data Sheets out and have them updated for the next day.... surely?

Just like my Christmas Cake mixture this year, some Data Sheets are lacking some consistency.

But all this has been said before and....
 
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holmedwa04

Member
Dippy said:
I've just been looking at the 28-pin Project Board Data Sheet axe020.pdf available right this moment from the Website an has been around for years.
I assume that is the document being referenced by holmedwa04?

Is this a typo?

And yes, it does say:
"The primary power supply (V1+) for the interface is a 6V or 4.5V DC. This is connected via the battery connector. DO NOT use a 9V PP3 battery, as the interface does not include a voltage regulator."

Note the "6V". Subsequent schematics also show 6V.

Whilst this is within a PIC "Absolute Maximum Ratings" it is beyond the recommended voltage range for the PIC (typically 5.5V for 16Fs). From the circuit schematic I cannot see any voltage limiting.

Running beyond 5.5V will mean that the PIC functions wil be running beyond spec and may affect some operations (e.g. frequency and logic levels).

Surely this should be changed to ".. for the interface is a 4.5V or 5V DC" in that document?
[i.e. all mentions of 6V to be changed to 5V]
People have obviously proven that it will work at 6V, but this is beyond Microchip's recommendation and also can confuse Users (and me) as to the PICAXE 'recommended' voltage supply,

Obviously, every Newbie will have read "Getting Started" Manual 1 page 5 ("At a Glance") where it says:-
"....4.5V or 5V DC is recommended. Do not use 6V, 7.2V or 9V"

Note the "Do not use 6V...."

I bit of consistency is required here perhaps.....?
A) It's not right.
B) It confuses and 'sends the wrong mssage'.
Click to expand...
Yes, thats exactly what it said on the data sheet, so I assumes 6V would be fine. As the receiver module that I am using has to be 5V I am using a regulator for this, because I don't want to blow anything up! So... I will use with a 9V plug in wall transformer and a 5V 7805 reg on each circuit board. This way I don't have lots of different supply voltages and plug in transformer is nice and easy to use.

Thank you for the clarification... I feel really bad for hijacking this persons thread and therefore wish to ask no more questions on this topic! I now have the knowledge I need :) But hopefully for anyone else who was unsure this little digression has been of use :p
 
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SilentScreamer

Senior Member
I've just tested the regulaor without any IC's on the board and I had 12V on both sides of the regulator. So I assume thats both chips blown and the regulator blown as well so I now have two questions.

Does it matter if the (I can't remember the correct names for them but) non-polarized capacitors are replaced with polarized ones for the voltage regulator?

And what is the maximum ampage that can be safely used on standard copper clad board (after I removed the ICs my 0V rail melted, I assume due to the ampage being too high)?
 
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Dippy

Moderator
Your 'average' polarised caps are fine for most simple linear stuff like this. Just make sure the voltage spec is OK. Best to be 'generous'; for the 12V side its good to err on the side of caution and choose a 25V cap.

However, some manufacturers make a bit of a fuss about capacitors and often make recommendations in their Data Sheets - so that is really your FIRST stop for reading up.
(Having said all that I sometimes, for prototyping, just chuck a couple of 10uF cheap'n'nasties into breadboards and have no major issues. But I'd follow the Data Sheet advice for pukka stuff)
Remember to observe the polarity markings on the component.

Oh dear. It sounds like there is something seriously wrong with your PCB or assembly.

Before making another one, can you highlight tracks on your CAD programme - just to see if one has flopped over another accidentally?

Assuming you didn't insert components incorrectly , or the components were unsuitable / duff, then the PCB is your culprit.
So, you've got to spend some time on it now with a multimeter and magnifying glass.

ALWAYS check a new PCB before doing soldering. Then, like I said before, build-a-bit and test before proceeding with the next stage. It's common sense really isn't it?


"And what is the maximum ampage that can be safely used on standard copper clad board.."?
- well x-hundred Amps if your tracks are wide enough. How long is a piece of string?

Tracks have resistance. Thinner/longer means more resistance. More resistance means more heat. Heat means hotter and that is the killer.

There are some calculators online, but here are a couple of examples from the Easy-PC 'Design Calculator':

(1oz copper FR4 outer layer track, for a 20oC temp rise under load)

0.3mm = 1.2 Amps
1mm = 3 Amps
3mm = 7 Amps
25mm = 33 Amps

These should be considered as 'good approximations' not absolute.
Other calculators may show variations, but so what.
And obv this refers to low-ish voltage DC-ish stuff!
 
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sketchy

New Member
sorry to be thick ad slightly off track but how do diodes reduce the voltage from 6 to 4.8 i thought that a diode was just like a one way gate?
Thnaks

Joe.
 
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SilentScreamer

Senior Member
Diodes drop about 0.7 volt (depending which diode you use). I have a voltage regulator however to take 12 volt down to ~5V though so the chip is safe.

EDIT: Refer back to post 69 for my unanswered question seeming as its now on a different page.
 
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sneaky

New Member
how to connect a picaxe circuit board to the computer using the usb to serial cable

i dont have the 9 pin serial port on the computer, but i have a usb port, the usb to serial cable and driver, after i install it, when i go to the program editor for picaxe, and click 18x, then download program (the cable is connected to the circuit board (usb to 9 pin serial plug to circuit board)) , it says some error, it wont connect using the cable. How do u make it connect?

the cirsuit board always has full power on, and works fine with other computers with the serial port originally there...
 
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SilentScreamer

Senior Member
sneaky said:
i dont have the 9 pin serial port on the computer, but i have a usb port, the usb to serial cable and driver, after i install it, when i go to the program editor for picaxe, and click 18x, then download program (the cable is connected to the circuit board (usb to 9 pin serial plug to circuit board)) , it says some error, it wont connect using the cable. How do u make it connect?

the cirsuit board always has full power on, and works fine with other computers with the serial port originally there...
Click to expand...
Sneaky, can you make a new thread for this as so I don't lose my questions to other peoples please.

Also are you using the PICAXE USB to 3.5mm audio jack cable or a USB to serial converter and then the serial to 3.5mm jack cable?
 
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