MOSFETS, SMARTFETS etc

[fritz42_male]

There have been a few threads lately about MOSFETS and so on.

How about a sticky thread that includes some of the nicer and simpler devices?

For example, are there any devices that can work at PWM speeds without a 'pump'?

Triacs suitable for PWM?

And so on. Anything that minimises the complexity of what we have to solder!

Maybe another thread for good buys. I recently found a UK site that will sell you 16x2 LCD displays at 10 for UKP11.50 ex postage

 

[Jamster]

If i had a pound for every time someone says: "How about a sticky"...

I have used standard MOSFETS for PWM in my lighting project with the standard interface circuit, nothing has gone wrong and no one commented on it when i posted the schmatic so i rekon thats ok.

I have kits that use a Darlington IC with PWM so guess thats ok, apart from the fact the kit didnt work...

As for SMARTFETS, FETS and Darlington pairs I have never used them so cant really comment (yes i have never used a darlington pair)

 

[Dippy]

The trouble is that a simple question like that requires a 5 page answer to be thorough.
... and that's after a bit of tooth pulling to actually get some understanding of what you mean.

For example:-
"... are there any devices that can work at PWM speeds without a 'pump'?"
1. What is your interpretation of PWM speed?
You could have 1 kHz driving a motor , but 200kHz for a SMPS.
Does 'pump' mean a proper driver?
Whether or you need a driver depends on the MOSFET and the frequency.
A driver isn't always a charge-pump design for N chan high siders.
And DO NOT believe anyone who says that their high frequency big fat high power nude MOSFET circuit is super-efficient without good driving.
It's cobblers.

2. "Triacs suitable for PWM?"
Are you referring to AC switching?
You really must read up on AC switching devices as they switch in different ways.
e.g. a brief trigger will switch them on for a cycle , therefore PWMing at silly speeds is pointless.


There are piles of SMARTFETs (word used generically).
Check out the spec to see if it is suitable.


"....16x2 LCDs at 10 for UKP11.50 ex postage"
They may be fine. You try them first eh?
On this , and other Forums , I have seen examples of tight-asses buying super cheap anonymous LCDs and GLCDs and then spending 10 pages Q&A trying to get them going. Sometimes with success and sometimes not.
You may get a great bargain. If so, yahoo , well spotted and tell us.
But, in principle, I think total novices buying cheapo, unknown LCDs from unknown suppliers is not ideal.
There's often a reason they're cheap. e.g. Dicky electrically or dicky controller etc.
Novices (and we all were once) struggle and if the LCD is a bit dicky or non-standard then it's an early bath.

 

[fritz42_male]

The trouble is that a simple question like that requires a 5 page answer to be thorough.
... and that's after a bit of tooth pulling to actually get some understanding of what you mean.

Not really, surely people can just mention a few devices that have worked well for them?

For example:-
"... are there any devices that can work at PWM speeds without a 'pump'?"
1. What is your interpretation of PWM speed?
You could have 1 kHz driving a motor , but 200kHz for a SMPS.

1KHz would be fine and Yes, pump in this instance means a proper driver to overcome gate capacitance in the shortest time possible. e.g. are there some decent logic level mosfets out there that can switch rapidly from a straight picaxe output (& yes, I know you are going to ask what 'rapidly' means - in this case maybe 1KHz switching)

Does 'pump' mean a proper driver?
Whether or you need a driver depends on the MOSFET and the frequency.
A driver isn't always a charge-pump design for N chan high siders.
And DO NOT believe anyone who says that their high frequency big fat high power nude MOSFET circuit is super-efficient without good driving.
It's cobblers.

2. "Triacs suitable for PWM?"
Are you referring to AC switching?
You really must read up on AC switching devices as they switch in different ways.
e.g. a brief trigger will switch them on for a cycle , therefore PWMing at silly speeds is pointless.


Thats what I mean - is there a nice logic level mosfet equivalent out there.

There are piles of SMARTFETs (word used generically).
Check out the spec to see if it is suitable.

Once I have a part number I can check the spec out but it's getting the part number in the first place. I am not immersed in the electronics world these days and companies are bringing out new products at a rate of knots. It's hard to find 'interesting' devices and all I was asking for was for people to suggest ones they had come across.


"....16x2 LCDs at 10 for UKP11.50 ex postage"
They may be fine. You try them first eh?
On this , and other Forums , I have seen examples of tight-asses buying super cheap anonymous LCDs and GLCDs and then spending 10 pages Q&A trying to get them going. Sometimes with success and sometimes not.
You may get a great bargain. If so, yahoo , well spotted and tell us.
But, in principle, I think total novices buying cheapo, unknown LCDs from unknown suppliers is not ideal.
There's often a reason they're cheap. e.g. Dicky electrically or dicky controller etc.
Novices (and we all were once) struggle and if the LCD is a bit dicky or non-standard then it's an early bath.

I know but in this case the only issue with the LCDs was the lack of a backlight - otherwise they are fine. Again, all I'm asking is for an ongoing easily accessible thread with suggestions on products that people had found. Searching through past posts is easy but time consuming.

 

[Jaguarjoe]

One man's meat is another man's poison. This is like commenting on autos. Some people love Jaguars, some love Beemers.

What is Rev Ed's liability when a vendor discovers his product being disparaged on this website? The Jaglovers website care takers were sued over this same matter and now ban all vendor comments, good or bad. When a lister comments on where he bought something, he will generally put a disclaimer in his post stating he is not affiliated with the vendor he bought from.

 

[william47316]

TRIAC's are used in AC electrics, if used in DC they will act like a thyristor (SCR) and latch on until the load is turned off plus they need some sync circuitry to switch at the right points in the waveform

 

[hippy]

What is Rev Ed's liability when a vendor discovers his product being disparaged on this website?

As with the example stated; we can be asked to remove such comments, be sued for damages and even have injunctions invoked against us, any breach of which would result in even more severe penalties.

We can argue they were not our views, are not responsible as 'publishers' for what users write, that what was written was 'fair comment' but the law and courts can see it entirely differently and defending an action involves cost and time. Any action, especially successful, can be severely damaging to reputation and the future of any company or body.

That's why we do moderate the forum and why comments are sometimes deleted or edited, or we will add follow-ups to balance what was written - The thread involving lead-free solder strayed dangerously close to suggesting it to be 'unacceptable' and responsible for accidents and deaths; without authoritatively tested evidence of that being indisputable fact it becomes mere assertion and potentially libellous.

As well as having to take responsibility for negative comments we also have to take responsibility for positive and favourable comments, if it's claimed we are endorsing such opinions, when things fail to measure up to expectations.

Then there's the whole area of safety, automotive electronics, mains power, projectiles and pyrotechnics, use of lasers and so on, with outcomes for which we could also be held responsible or liable for.

Basically we will be first in the firing line when someone takes exception to anything written here or seeks redress. That's why we have to be careful over everything including language, especially profanity and swearing; we need to respect the diverse audience we have.

It's a delicate path that needs to be walked and we hope that users of these forums will respect and understand that. We have responsibilities and duties which we have to take seriously with potentially severe consequences if we do not. At the proverbial end of the day it is, "once bitten, twice shy", and if certain things are creating problems it's usually pragmatic to simply ban discussions of such things completely.

 

[Dippy]

This gets asked about so often that maybe you should summarise it and put it in the FAQs.
A good writer could make it succinct.

Whilst you're at it, make the T&Cs more comprehensive and make them more accessible.
I've seen many other Forums with much more comprehensive T&Cs which are much better at covering bottoms.

After all, if the moderators all got run over by a bus tomorrow there wouldn't be anyone to slap wrists and delete stupid things.

IMO if a Forum user said something dodgy and your bottoms were covered in T&Cs to the best of your ability and within the law I doubt if any Court in the land would take Rev-Ed to task.
It's not like a Newspaper where , in theory, an Editor has checked it an officially passed it.

I feel that more than half of the liability-related comments are based on guess (albeit well intentioned and logical). Get a lawyer drunk and get the real info.