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Microchip's TB008 Reprise

**Hi to all:

On March 13 this year - poster " Hammy" raised a few valid questions about Tech Bulletin " TB 008 " on the Microchip web site ( and quoted widely elsewhere) on the subject of "Transformerless Power Supplies".

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This prompted Mr Rod Elliot of ESP to contact Microchip with a view to having them retract and withdraw TB008 from publication. As feared but expected, this was not successful.

The ESP site now has an outline of what happened when he complained and includes the email reply received from Microchip's Tech Support Group.

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A second, even stronger worded email from Mr Elliot went unanswered.

Microchip's anonymous tech support guy was clearly WAAAY out of his depth on the topic of AC mains and appliance electrocution hazards - as was that fool Stan D'Souza who wrote the infamous tech bulletin.

D'Souza is now a "Technical Fellow " at Microchip - so I guess the dude walks on water and his word is Gospel round the place.

IME - people like him will * NEVER * admit to even the most grievous of errors nor allow any error of theirs to be publicly corrected.

Shame there appears to be no way to make direct contact.

..... Phil

Reply to
Phil Allison
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Unbelievable!

There is a way to make direct contact though, and right to the TOP. Steve Sanghi is Microchip's CEO, his direct email address is (spambot friendly): steve DOT sanghi AT microchip DOT com

Well, maybe his personal secretary vets every email first, but it should at least get that far.

Dave.

Reply to
David L. Jones

and tell him how much you love his book:

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Dave.

Reply to
David L. Jones

and tell him how much you love his book:

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Dave.

Reply to
David L. Jones

That supply is very dangerous in the wrong hands. But I've been using caps to run LED pilot lights on 120 with no problems. It is just not suitable for any application where the user might come in contact with the "low voltage" derived from a capacitive reactance power supply.

I've got one in my electric range - powers a microchip pic to modulate the range heater - no more dangerous than the 240 VAC mechanical switch it replaces.

The problem is in the application, not the circuit I'd recommend for anyone just starting out in electronics. After a couple of "sit down" shocks you gain the proper respect for mains.

I'm pretty sure he didn't become a technical fellow because of this circuit - it appears in a 70's Fairchild publication.

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Reply to
default

Well, they should clearly be more responsive about these kinds of things. However, I'm still somewhat confused as to why the original tech note is considered harmful.

It seems to be a fairly standard transformerless power supply. I've built lots of them. The only problem with it is that it lacks a fuse (other than the silly one between neutral and earth). The circuit needs to be isolated from the user, of course.

I wonder if Australian and US standards are different in this respect?

Regards, Bob Monsen

Reply to
Bob Monsen

Here is my thread in the Microchip forum. I posted it in their "Tips 'n Tricks", but under the development tools rather than a more hardware-oriented area. Still, it is usually read by their technical people, and I think it should be addressed.

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Maybe someone should contact a lawyer and tell them they tried a circuit recommended by Microchip, and got a bad shock, and now they have neurological problems. It would be hard to disprove, if you actually built the circuit and just claim to have touched it. You could also offer to submit a design to Microchip for one of their contests as "The Next Killer App"!

I like Microchip, but that App Note needs some major revision or retraction.

There is also a bad circuit in:

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It is Tip #8, and it shows the AC line directly connected to the +5VDC supply, and the dropping capacitor and resistor on neutral!

This sort of supply is reasonably safe if dropping resistors and capacitors are used in both legs (if line/neutral polarity cannot be guaranteed), or for 220 VAC applications, AND if the maximum current to ground (or into a person connected to ground) is less than about 10-20 mA. The 0.47 uF capacitor shown in their circuit will limit current to about 21 mA at 60 Hz, so if there were one on each leg, it would be reasonably safe.

Paul

Reply to
Paul E. Schoen

The simpering wimp doth speak. Let me guess, you are one of the children who never got to be playground monitor and it has affected you this way. You'd probably be wetting yourself if you had to confront some of these people in person.

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Reply to
default

"default = some anonymous mental retard "

** Fuck off and die

- you vile, autistic pile of shit.

..... Phil

Reply to
Phil Allison

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