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Re: Driving Triac Directly with 555 Output?

>>Obviously beating a dead horse since the OP admitted his quest was

>>bogus but, just for for fun, here's how to do it with a four quadrant >>triac, no opto, and no full-wave bridge: >> >>.AC>--+-------------------------------------+ >>. |A | >>. [1N4002] | >>. | | >>. | 78L05 | >>. +-I O-+-------------+---------+ [LOAD] >>. |+ G | | | | >>. [C1] | [R1] |8 | | >>. | | | +----+----+ | | >>. +---+ | | Vcc _| | | >>. | +-----7-O|D R|O-4-+ | >>. | | | | MT2 >>. | [R2] +--6-|TH OUT|-3-[R3]---G >>. | | | |__ | MT1 >>. | +---+-2-O|TR 555| | >>. | | | GND | | >>. | [C2] +----+----+ | >>. | | |1 | >>.AC>--+-------+-------------+---------------+ >> >>--- >>JF > >Most triacs are not spec'd to fire in quadrant 4. > >John
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You said that earlier, and it's true enough, but irrelevant.

Did you not read the text preceding the schematic?

Here, I'll post it again:

"Obviously beating a dead horse since the OP admitted his quest was
bogus but, just for for fun, here's how to do it with a four quadrant
triac, no opto, and no full-wave bridge:"

Notice the reference to a four quadrant triac?

Something like one of Teccor's "L" or "O" series triacs at: 

http://www.littelfuse.com/data/en/Product_Catalogs/PowerThyristorDataSheets.pdf

would work nicely.

Using the "L" series would allow the use of a 7555 and greatly reduce
the size of C1.
Reply to
John Fields
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Can you fix it?
Reply to
John Fields 

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More of your bullshit???

Which people, which circuits, and why aren't they reliable?
Reply to
John Fields

Most of the flaky unreliable stuff I see posted here, is posted by Larkin. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

Look at a triac data sheet. The bit about "quadrants."

John

Reply to
John Larkin 

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You really don't want to get specific enough to get nailed, do you?
Reply to
John Fields

Please pay attention and don't start clucking half-cocked.

My point was to be careful about quadrants. Some triacs trigger in all four quads, but a lot won't.

John

Reply to
John Larkin

WHY do you keep feeding him, ad nauseam? ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson 

--
So he won't die?
Reply to
John Fields 

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All poppycock.

For the record, at the start of this thread the OP asked if he could
get rid of the opto and, after an initial flurry of excitement, I
posted a schematic which showed him a way to satisfy that desire and
allowed him to get rid of the full-wave bridge as well.

In the text portion of my post I indicated that the triac needed to be
a 4 quadrant device and you, curiously horning in on the act, stated
that there are more 3 quadrant triacs available than 4 quadrant.

Totally irrelevant, since 4 quadrant triacs are easily obtainable and
I specified that a 4 quadrant device was needed to make my circuit
work.

Phil and I both pointed out sources of 4 quadrant triacs, but you were
hooked and had to have your say, even though it wasn't germane.

So, time went by and you've tried all sorts of nonsensical nefarious
devices to try to discredit me, and anyone else who's at odds with
you, but you haven't commented on my circuit, with which you seem to
be at odds.

Chicken?
Reply to
John Fields

Careful with too close connection of chips and a triac gate.. the gate pin isn't completely benign.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

Die, baby, die! ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

Shit ?:-) ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

      Remember: Once you go over the hill, you pick up speed
Reply to
Jim Thompson

All your circuits are 555 circuits. My main objection with them is that, well, they are all 555 circuits.

John

Reply to
John Larkin

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The MOC3010/3020 series of opto triac drivers are cool. They solve a bunch of problems.

John

Reply to
John Larkin

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I think you might fix it by just moving the anode of D2 (1N4007) to the AC line connection at the fuse (F1).

-Bill

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=A0 MT2 =A0

MT1 =A0 =A0 =A0 =A0

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=A0| =A0 =A0 =A0 =A0 =A0 =A0

=A0 =A0 =A0 =A0 =A0 =A0

=A0 =A0| =A0 =A0 =A0 =A0 =A0 =A0

Reply to
Bill Bowden

Not exactly sure what you are trying to point out here but a Q4 will fire either way as long as there is current in the gate through A1(MT1).

My comment was based on the fact of induction kicking back through the sink mode of the timer.. Seen this kind of circuit and it causes miss fires a long with damage if the voltages are too high. Hence the reasoning for using Opto's. Using an Emitter follower is still better than using a direct link like this, at least it removes some of the return path to the gate, when off.

Years ago (~25), I redesigned a Siltronics EDM drive and sensor controls. The supply had a CT source so I simply used a bridge rectifier on that source and 2 Q4 Triacs being driven via 2 555's using a phase angle trigger from the supply to control speed. I made several trips there replacing the 555's over a period of 6 months before I understood what was going on. I ended up using the 4N24 family type to fix the problem by isolating the 555 from the triac gate. I was able to duplicate the problem by jerking the attached DC motor up/down rapidly there by, causing the DC motor to back generate some voltage.. This motor had snubbers and large chokes on it but still didn't fix this problem..

When It was finished, the new drive, PID and sensor electronics occupied only 1/4 of the real-estate over the original drive. As far as know, that machine still runs today! Back in those days, we didn't have a lot of Triacs you could depend on not latching up. Today, they are getting much better.. But I still have doubts about using them in a quad type output bridge.

Then there was the Cincinnati EDM, that is another story, 3-400Z's

Jamie

Reply to
Jamie

I know how that is, we have a load of 50 amp Q4 studded types that has issues where only 1 out of 4 will fire properly in all quadrants at their prescribed 100 ma trigger. The failed one's have at least 1Q that requires like 250ma or more to fire. Must of been some fire sale I got them from!

Jamie

Reply to
Jamie

They don't seem to be too worried about that. It's evident.

Jamie

Reply to
Jamie

YEs, I've used those types a lot in pure AC circuits, they do work nicely. The old 808 Eurotherm PID controllers use those for the AC output option card to drive the Triac.. Our plant still uses lots of those units so we keep them on hand. What's nice about those controllers are, we can make our own little output interface and the processor does not know the difference :)

Jamie

Reply to
Jamie

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