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Old 24th Mar 2011, 11:32 pm   #81
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Default Re: Solid State Vibrator.

I tried that and it didn't work for me. See post #12.
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Old 25th Mar 2011, 7:32 pm   #82
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Default Re: Solid State Vibrator.

The 555 is a bad choice in this application because it has an inherently uneven mark-space ratio. Try using a 4047; which has a bistable and mono/astable in one package. The bistable output will have a mark-space ratio nearer 1:1, as the total charge + discharge time of the R-C circuit sets the duration of each phase, aot the charge and discharge periods each setting the duration of one phase.
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Old 27th Mar 2011, 11:44 pm   #83
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Default Re: Solid State Vibrator.

Which is exactly what I used see post #56.
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Old 19th Mar 2012, 9:09 pm   #84
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Default Re: Solid State Vibrator.

I've always used a simple 2 bipolar transistor circuit but have problems keeping the transistors cool - they just don't turn on and off sufficiently well and thus dissipate heat! I thought I'd try your Mosfet circuit - it's absolutely fine, wished I'd seen it before. The devices are so firmly "on" or fully "off" that there are virtually no losses and there's no heating up at all! A minor problem is that such is the efficiency that my HT is about 20% too high, but I can get over that. A really good circuit - thank's so much for publishing it on the forum.
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Old 20th Mar 2012, 11:35 am   #85
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Default Re: Solid State Vibrator.

Thanks for your vote of confidence Colin. I really can't take much of the credit though. The circuit was a result of online cooperation between many forum members.

My own version continues to function reliably.
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Old 20th Mar 2012, 12:20 pm   #86
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Default Re: Solid State Vibrator.

I've made three of these now and they've all worked first time and without generating any heat. I've made a few modifications to the pcb design and if anyone wants a copy of the artwork for this please just PM me.
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Old 9th Sep 2012, 10:19 am   #87
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Default Re: Solid State Vibrator.

Hello everybody,

I've got an old vintage radio Blaupunkt from a Mercedes. A friend of mine asked me if I could repair it for him. When I opened it, the vibrator was missing. So I starting browsing the NET and I found this forum. I have built-up SSV with the 4047 and is working great. I would like to say Thank you to everyone who went to the trouble.

I have attached two EAGLE files of SMD versions. They both are working perfect.
Also I have few a PCB's left if anyone is interested I can post them. Please let me know.

George
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Old 9th Sep 2012, 8:35 pm   #88
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Default Re: Solid State Vibrator.

NE555 can be made to do 50/50 duty cycle. Just take a resistor from pin3 to the top of the timing capacitor, and remove the other two resistors from the timing circuit and disconnect the discharge pin- you have a 50% circuit with a single NE555 and one resistor and one CAP. If you need an inverter out of an NE555 no problem, just feed the output of one NE555 into the input of the other one with the discharge.

In form +V to pins 4 and 8
ground to pin 1
pins 2 and 6 to junction of R and C
Other pin of C to ground
other lead of R to pin 3.

Gives 50/50 duty cycle

As an inverter

Input to pins 2 an d6
pin 3 output
pins 4 and 8 to +V

Hope that helps.
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Old 9th Sep 2012, 11:18 pm   #89
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Default Re: Solid State Vibrator.

Connecting the timing resistor of a '555 to the output will give approximately 1:1 M/S ratio but there are two problems with this...

The output + and - saturation voltages are not equal which will offset the M/S ratio.

The tolerance of the switching thresholds ( nominally 1/3 and 2/3 supply) is over 10% leading to a larger tolerance on the M/S ratio.

Using the '4047 with its built in divider guarantees a practically perfect 1:1 ratio.

Since any deviation from 1:1 will give a DC component in the inverter transformer leading to possible core saturation,
the '4047 is preferable for this application.

Jim
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Old 9th Sep 2012, 11:41 pm   #90
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Default Re: Solid State Vibrator.

I'd still avoid the 555 like the plague.

The plain old bipolar 555 has a design fault in it. One one edge of output transition, it tries to turn on both the top and bottom of the totem-pole output. This drags a large pulse of current out of the power supply decoupling capacitor, and during the transition it goes through an oscillatory period where the output hives a burst of fast pulses.

I've come across this burst causing serious drama in power supplies. Also, if you ever use a 555 to clock logic you'll come across the effects of multiple clocking, making counters seem crazy. The CMOS 555 variant is OK, but tests showed that several makes of bipolar 555 were all dodgy.

It's a well known flaw in the design community... I think Horowitz and Hill mention it, but it doesn't seem to be known hereabouts.

David
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Old 10th Sep 2012, 12:19 pm   #91
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Default Re: Solid State Vibrator.

Agreed, I wouldn't bother using a 555. By the time you've done the necessary hacks to get it to behave itself, you've already negated the advantage of the monolithic IC. In an analogue circuit there's usually a spare op-amp you can use to build an oscillator, and in a digital circuit there's usually a couple of NAND gates you can use for the same purpose. The 4047 has a built-in divide-by-two, which should give you a 1:1 mark-space ratio.
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Old 16th Sep 2012, 4:22 pm   #92
Colin Boggis
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Smile Re: Solid State Vibrator.

Best circuit I've found uses the 4047 and two mosfets. I've built them for both positive and negative ground radios. Seem to work fine in most sets although sometimes you need to play with the capacitor value across the transformer. The circuits I use and board layout are attached (I don't claim originality for them)
Attached Files
File Type: pdf 12V Car Vibrator pcb.pdf (420.0 KB, 676 views)
File Type: pdf 12V Car Vibe Neg Earth final.pdf (389.4 KB, 874 views)
File Type: pdf 12V Car Vibe Pos Earth final..pdf (379.5 KB, 468 views)
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Old 23rd Sep 2012, 12:30 pm   #93
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Default Re: Solid State Vibrator.

If anyone is contemplating putting a new SSV together, I can recommend that they take a look at Georger's post (post 87) offering PCB's. As it's that time of year when I am frantic trying to finish all the work on the house/cars/garden that I should have done sometime during the last 6 momths , I contacted Georger, and for a few AUS$ ended up getting two fully assembled SSV's from him. His PCB's are formatted for SMD components, so far too hard for an old fogey like myself to deal with!

Last edited by Bazz4CQJ; 23rd Sep 2012 at 12:35 pm. Reason: typo
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Old 2nd Oct 2013, 1:27 pm   #94
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Default Re: Solid State Vibrator.

Hi everyone,
After while I am coming back with the SSV design.
You have to download a EAGLE (http://www.cadsoftusa.com/) to view the design.
Have fun.

Georger
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File Type: zip Solid State Vibrator.zip (53.5 KB, 411 views)
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Old 2nd Oct 2013, 2:49 pm   #95
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Default Re: Solid State Vibrator.

A side-thought: has anyone building a SSV experimented with placing a suitable capacitor across the secondary of the transformer (so making it a tuned-circuit) then varying the 4047 frequency to find the point at which it matches the resonance of the transformer's tuned-secondary?

I remember that back in the days of mechanical vibrators there was often a very-odd-value high-voltage capacitor fitted across the secondary - whether this was to tune it to about the same frequency as the vibrator's reed, or for something else [spark suppression?] I'm not sure. It makes me ponder whether those who have had success with SSVs have done so because they've serendipitously had the oscillator frequency near the natural resonance of the transformer, and those who've been less-successful have been trying to force the transformer to do its thing at a sub-optimal frequency?
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Old 2nd Oct 2013, 8:46 pm   #96
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Default Re: Solid State Vibrator.

I very rarely have success with zip files. What is their purpose?

The original mechanical vibrators had a dead zone where the polarity was changing over. By putting a capacitor in the circuit, the polarity will change ready for when the contacts are made. Since the dead time is only a small proportion of the total cycle time, then the resonant frequency must be much higher than the vibrator frequency.
The effect should be to reduce contact sparking and wear.
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Old 4th Nov 2013, 5:35 pm   #97
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Default Re: Solid State Vibrator.

Hi guys, I've just noticed this thread after a while away from the forum - hello! I have some experience from another project that may be relevant here.

As mentioned by mhennesy, MOSFETs can overheat if the gate drive is insufficent but are just fine if driven hard enough. For example, I've just made a class E RF amplifier based on a switching design with a crystal and a very competent driver, the IXDD414CI.

Class E is obviously irrelevant at multivibrator frequencies, but worth noting that high-powered MOSFETs such as the IXFH16N50P(http://ixdev.ixys.com/DataSheet/99357.pdf) can switch up to 4Mhz with no problem -- way, way beyond the requirements of a solid-state multivibrator. The rise and fall times are each around 25 nS and the dead time only has to be an incredible 70 nanoseconds before the device can safely conduct again.

Anyway, hope my experience with that driver may come in handy for others. The component count for a vibrator would be minimal - crystal oscillator, some decoupling components, a zener, the driver, a couple of resistors and a ringing LC switched on and off by the MOSFET to provide HV output.

The IXDD414CL driver is very easy to configure - only input, output +12v and ground pins are needed.
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Old 5th Nov 2013, 11:42 pm   #98
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Default Re: Solid State Vibrator.

May I also suggest something? the SG3525 and many other clones (KA3525) etc are fully controllable half bridge PWM drivers, usually used in Car audio amplifiers. Not fixed at 50% duty so if your system isn't resonant then you can make substantial savings on primary current.


Cheers, Dave.
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Old 24th Jan 2015, 10:07 pm   #99
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Default Re: Solid State Vibrator.

Many thanks for this!

A friend of a friend wanted his Radiomobile 20x fixing, so after replacing several capacitors and converting the selenium bridge to 1N4007s I turned my attention to the vibrator (type Plessey 1412). Cleaning the contacts made it work again and I was rewarded with R4 LW coming in loud and clear.

It was the first time I have seen a vibrator supply and was a bit surprised by the noise - noiser than my Alfa, and that's a diesel! No idea what the owner's MGA sounds like though. Was thinking to build up a boost regulator and bypass most the the HT supply section in the radio, but then came across this thread when looking up info about vibrators.

I used basically the circuit in post #92 but made some parts surface mount and built it on veroboard. The FETs are type FQD5P10. They run cool.

Once again thanks very much for this idea.

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Old 25th Jan 2015, 11:18 pm   #100
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Default Re: Solid State Vibrator.

Quote:
Originally Posted by astral highway View Post
"The IXDD414CL driver is very easy to configure - only input, output +12v and ground pins are needed."
Looked for this but found it marked as obsolete, replaced by IXD614:

http://www.ixysic.com/home/pdfs.nsf/www/IXD_614.pdf/$file/IXD_614.pdf

Hope this helps

Best wishes
Guy
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