Download circuit - BAT85 alternative

N

nbw

Senior Member
For the piddly cost of a 0.1uF ceramic cap, you should always slap one between the power rails of every IC. Often you can sneak them under the IC on the circuit board, between the rows of pins. It will (should) become 2nd nature after a while :)
 
A

amewsaj

Member
It is not the cost, but the distance to get to a shop with these components. Too expensive to order online (postal service)

Is it really that important?
 
A

amewsaj

Member
And why so important. If it works just fine without it, and nothing gets overheated or anything, why then needed?
 
E

eclectic

Moderator
amewsaj said:
And why so important. If it works just fine without it, and nothing gets overheated or anything, why then needed?
Click to expand...
I'll leave it to the experts, but, see post #30
and, every Picaxe project board has them fitted.
My AXE091, for example, has seven 100nF fitted.

e
 
hippy

hippy

Ex-Staff (retired)
amewsaj said:
And why so important. If it works just fine without it, and nothing gets overheated or anything, why then needed?
Click to expand...
It's a bit like wearing car seat belts or looking to see if there is any taffic coming before you step into a road - You may not always need to, can often get away without doing so, but under different circumstances they are necessary to prevent adverse effects and therefore recommended.
 
B

BeanieBots

Moderator
amewsaj said:
And why so important. If it works just fine without it, and nothing gets overheated or anything, why then needed?
Click to expand...
Does your circuit work just fine?
If your circuit is working PERFECTLY all the time and never glitches (or you don't mind the odd miss-count) then fine, leave them off.

The home PC market is extremely competative. Every penny counts.
Do they fit them? YES THEY DO.

Do they think it's worth the extra money? YES THEY DO.
 
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amewsaj

Member
The miss-count was only while doing serial stuff.

I have let the program run for some time, and suddenly I see that one of the chips like changes state, and seems to freeze. Could this be due to the decoupling missing?
 
B

BeanieBots

Moderator
Yes, it could be.
Then again, it might not. It could be a circuit error.
Until you fit them, you won't know.

The simple solution is to eleiminate the OBVIOUS things first.
Erratic behaviour (besides basic circuit errors) is more often than not caused by noise. Decoupling capacitors make a major contribution to noise elimination. Circuit layout is another significant factor. It's not as simple as connect one pin to another. The length, path and neigbouring signals are also important.
 
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amewsaj

Member
Ok, this was a DOH problem as well...

One of the wires from external sensor was loose and suddenly touched a pin on the chip directly. This means whenever the sensor was active, the chip received 5V on a wrong pin.

Problem solved.

So no, I have no issues without decoupling, except for the serial noise problem. But in the amount it is used, it does not seem to be a problem. For now, I will leave decoupling off.

Anyway, if I decide to do it, is it correct that I put a 100 nF ceramic capacitor between the 5V and 0V pin on the chips?
 
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