Making a project at GCSE

I

IblalRakha

New Member
Hi, I'm doing a GCSE project which is making an alarm.

I would like to know if i should use a 555 timer in my circuit or an 08M chip.

Any help? Thanks.

Iblal Rakha
 
B

BeanieBots

Moderator
That would depend on if your GCSE project needs (or if you want) to include any software.

P.S.
I've moved your thread from the finished projects section to the active forum for you.
 
Last edited:
I

IblalRakha

New Member
I was just wondering whether an 08M h as more advanteges than a 555?

Because programming would be more work, but a 555 won't let me be as expansive as an 08M would. Any help with advantages and disadvantages?
 
W

westaust55

Moderator
project at GCSE

More explanation about how your project should work would be helpful in answering your question better.

A 555 is a single timer and needs hardware changes to alter the time.
A PICAXE 08M is easily adjusted.
But do you want a simple delay time? or
should other actions happen while the timing phase occurs?

How about uploading a written description of the process flow and decision mechanisims that your alarm will have.

Anything is usually possible if the project definition is provided. We can help you but may not do you project for you.

EDIT:
Ah you came back with a response while I was typing.

Seems you just want a list of the pro's and con's for each chip. It that right?
 
A

Andrew Cowan

Senior Member
You'll get more marks with an 08M - a 555 counts as one block. A monostable controlling an astable counts as two blocks, which you need to get a good mark.

An 08M can count as lots of blocks, as you can program in as much as possible.

A
 
M

manuka

Senior Member
I spent decades with 555s (which were of course devised 1973), & still feel everyone in electronics should get to know this industry veteran. However-with a PICAXE,you'll now not only LEARN more & complete the project sooner, but also have endless scope for "Mmm- let's try it this way" software tweaking. Hence GO PICAXE!

Grown men can be reduced to drink/tears (or both) trying to make 555 circuits do what they want, as EVERYTHING has to be supplied as hardware. If you're out of (say) high value resistors & capacitors for perhaps longer timing intervals, then "TOUGH". With a PICAXE-08(M) all you need to do is modify a few items of high level code- it's so easy that you'll probably weep (with joy!). Stan

EXTRA: Quite aside from the above, the micro programming skills & insights you'll gain will be exceedingly valuable. Electronics today is characterised by software driving of hardware of course.
 
Last edited:
S

SilentScreamer

Senior Member
Cost: The cost of an 08M is very little extra compared to a 555. Don't forget that with a 555 you also need the capacitor, and several resistors. An 08M only needs 2 resistors. Also what price can you put on a decent GCSE grade that you keep for life (mine has cost a scary amount (I have got a over the top a bit :p) but we wont go into that).

Programming: This is reasonably simple, the software is free, the manual is great and you can ask any questions here, we're all happy to help (and between the oldies you'll never get a question that can't be solved with enough work :D). The time saved on designing a simpler circuit will probably make up for the extra programming time.

So its down to if you're willing to put extra time into doing the 08M route. It will result in a project a million times better and far easier to design.

Do you have a rough project ideas?
Also when does this project have to be done for? If you're in year 11 could have time to take into account, if you're in year 10 you have plenty of time to get it done...
 
Last edited:
S

SilentScreamer

Senior Member
Andrew Cowan said:
What's the project?

By the way, I am 100% sure it has not cost more than my A level project...

A
Click to expand...
It was an alarm with LCD display and it was going to have a PIR but I couldn't get it to work so it was abandoned. I destroyed a LCD firmware chip, a 16X2 LCD and a 28X1 with my first PCB attempt (it taught me to always double check it though so I don't mind). The end figure for it is about £100 :eek:

What's your A level project? I wish I had the option to do A level, not one of the ~10 schools near me offer it.
 
J

jglenn

Senior Member
Here is an idea, may not be trivial, but would be useful for my lab bench. :rolleyes:

A PICAXE power source! Use PWM to run a FET, that chops to create a 40V, 2A max DC output, filtered to a certain extent. It could be open loop to start.

That means there is no feedback, as in using the ADC input to compare the actual output to the commanded one, and using negative feedback to correct.

It would be nice if adjustable in 0.1V increments, and be settable thru some kind of PC interface, plus readback the actual voltage on the screen. This would exercise a variety of software and hardware, and actually help in making circuits. For extra credit, add a current limit/constant current mode, for safety and charging some batteries, like lead acid, nicad, and NIMH.
 
S

SilentScreamer

Senior Member
jglenn said:
Here is an idea, may not be trivial, but would be useful for my lab bench. :rolleyes:

A PICAXE power source! Use PWM to run a FET, that chops to create a 40V, 2A max DC output, filtered to a certain extent. It could be open loop to start.

That means there is no feedback, as in using the ADC input to compare the actual output to the commanded one, and using negative feedback to correct.

It would be nice if adjustable in 0.1V increments, and be settable thru some kind of PC interface, plus readback the actual voltage on the screen. This would exercise a variety of software and hardware, and actually help in making circuits. For extra credit, add a current limit/constant current mode, for safety and charging some batteries, like lead acid, nicad, and NIMH.
Click to expand...
I don't know about IblalRakha's experience or electronics knowledge, but I expect that's a bit much. In my GCSE class the general project is a 555 or 08M pulsing a decade counter. Where the 08M has one or maybe two inputs.

As a realistic project how about having an LCD display, its easy to code for if you use this to link it to the PICAXE. The circuit that is suggested in the datasheet works perfectly and is simple to use.
 
A

Andrew Cowan

Senior Member
jglenn said:
Here is an idea, may not be trivial, but would be useful for my lab bench. :rolleyes:

A PICAXE power source! Use PWM to run a FET, that chops to create a 40V, 2A max DC output, filtered to a certain extent. It could be open loop to start.

That means there is no feedback, as in using the ADC input to compare the actual output to the commanded one, and using negative feedback to correct.

It would be nice if adjustable in 0.1V increments, and be settable thru some kind of PC interface, plus readback the actual voltage on the screen. This would exercise a variety of software and hardware, and actually help in making circuits. For extra credit, add a current limit/constant current mode, for safety and charging some batteries, like lead acid, nicad, and NIMH.
Click to expand...

I'm in the middle of maying this (using a 30V, 4A transformer). I am using opamps to compare the actual voltage/current, with the voltage/current given out by the PICAXE (via an DAC).

A
 
R

Rickharris

Senior Member
IblalRakha said:
I was just wondering whether an 08M h as more advanteges than a 555?

Because programming would be more work, but a 555 won't let me be as expansive as an 08M would. Any help with advantages and disadvantages?
Click to expand...
555 timer can make a suitable noise - 556 wil make a good siren google for circuit. Combine with a thyristor latch for a simple alarm circuit.

08M will make a noise that needs amplifying to be useful alarm, will allow you to minimise the extra circuits needed to cater for the logic to make the alarm work.


555 + thyristor perhaps 50P 08M perhaps £1
 
D

Dippy

Moderator
Assumimg you're not going to use really high frequencies, I'd plump for the 08M.

The extra cost really is peanuts. The amount of programming will probably be peanuts. And software is often easier than hardware.
If I was transported back decades back to school and had to do a project there would be no dithering at all as to my choice.

And, of course, post-GCSE you can use it for something else....
If anyone is worried about a 50p saving on a one-off project then that is just so sad.;)
 
M

manuka

Senior Member
Dippy- well said!

As an aside -science/tech budgets can be so tight that an extra 50p per pupil may break them. I helped a NZ school back in 2007, which had assigned their ~200 11-12 yo. "Electronics" students just ~£1 per head to cover EVERYTHING needed- wire/solder/batteries etc etc. It was all we could do to afford an AA cell for a take home project. Admin. priorites of course, as the same school had no troubles sending a kids cultural group off to Japan for 2 weeks.
 
S

SilentScreamer

Senior Member
manuka said:
Dippy- well said!

As an aside -science/tech budgets can be so tight that an extra 50p per pupil may break them. I helped a NZ school back in 2007, which had assigned their ~200 11-12 yo. "Electronics" students just ~£1 per head to cover EVERYTHING needed- wire/solder/batteries etc etc. It was all we could do to afford an AA cell for a take home project. Admin. priorites of course, as the same school had no troubles sending a kids cultural group off to Japan for 2 weeks.
Click to expand...
Our school makes pupils pay for projects, though it never leaves teachers...
 
D

Dippy

Moderator
Good.
If you or parents have to pay for it then maybe it will be given greater respect.

At my old Grammar school parents had to pay for certain text books and sundries and any breakages/trashing had to be paid for by parents.
 
S

SilentScreamer

Senior Member
Dippy said:
Good.
If you or parents have to pay for it then maybe it will be given greater respect.
Click to expand...
Hardly, wire strippers to "trim" soldering iron nibs, solder balls even my 12V lead acid battery often has wire wool placed on it and even had a large paper clip placed across the terminals and now has two melted paper clip marks in it. The vast majority of my electronics class smoke, spend all night drinking on parks and compete for getting the most U grades. They all saw electronics as an easy subject.
 
D

Dippy

Moderator
Lordy, sounds like a disaster zone.

Ah well, no respect, pathetic, but hopefull it'll cut down wasting my taxes ;)
 
B

BeanieBots

Moderator
Don't think they exist any more, but in my school days, the interior bulbs used on buses and trains were the same BC fit as regular 240v bulbs but only rated at 24v. These would make a very spectacular flash when used as "replacements". It was such a common trick that teachers knew not to put the lights on before checking if they entered a dark classroom.
 
S

SilentScreamer

Senior Member
A apprentice electrician that use to go to the school decided to donate something he did for his apprenticeship to the school. It was an model ringmain with fuses, plugs and lights. It is all powered off a car battery for safety and to show the plugs working it has 12V car bulbs which have 3 pin plugs connected to them.

Of course school never had chance to rewire it a little so earth was actually +V (I told them they should) so it proved too much temptation for someone...
 
B

boriz

Senior Member
I’ve got that beat!

As a teenager, I got into CB radio for a while. I powered my base from a car battery on my desk with a charger always connected. (Yes I know, dumb). While chatting on the CB one day, I thought I’d make some sparks using a bit of left over co-axe cable.

The hydrogen ignited, the battery exploded. The top and one side of the battery was almost completely gone (shattered all over the room), and there was acid everywhere. I was stood with my face directly over the battery, maybe 1 foot away, certainly less than two.

Not a scratch! Not a sting!. Not one drop of acid on my face! (My clothes were a different story).

Months later I was still finding sharp shards of battery casing behind wardrobes etc. I still clearly remember the sensation of hot exploding gasses around my head.

Ah. Teenagers….
 
S

SilentScreamer

Senior Member
Wow!!! Can I say anymore?

A few weeks ago a took apart an extension lead without unplugging or turning it off. I had removed live neutral and earth before realising, I jumped a mile when I realised (with live an neutral both touching my fingers). Not a single shock somehow.
 
J

jglenn

Senior Member
Andrew: I'd like to see any code and schem on the power supply that you can post. It is an obvious project. Is there an easy way to process data sent over the serial port from the PICAXE with the debug cmd, or a terminal emulator? Short of using Visual Basic to make slick meters on the PC screen, and other objects (I never used VB). Looking for fast, easy solutions, not a lot of custom pc code.

My current homemade supply is about 30 years old, uses the LM10 (no one will remember it), a chip with an opamp and ref. One controls volts out, the other current. The schem is right out of a National Semi databook. I did find that when charging batts, you must go thru a diode, or it can blow the whole thing up.
 
R

Rickharris

Senior Member
SilentScreamer said:
Hardly, wire strippers to "trim" soldering iron nibs, solder balls even my 12V lead acid battery often has wire wool placed on it and even had a large paper clip placed across the terminals and now has two melted paper clip marks in it. The vast majority of my electronics class smoke, spend all night drinking on parks and compete for getting the most U grades. They all saw electronics as an easy subject.
Click to expand...
Change schools - There will be a vacancy at my school in 18 weeks!
 
You must log in or register to reply here.
Top