Muller Dynamo

[romerouk]

This is the place I was thinking to have the 10-20k resistor
I know it is a simple circuit but for simple projects it works quite good

I think that some people are not realizing how this Hall type works. There other types where you have plus at the output, this one works with negative.

[romerouk]

Hi Folks,

I included below a modified schematic of Romero, and I inserted a series resistor between Hall Pin 3 and transistor base to limit the collector current of the Hall's output transistor and the base current of the PNP transistor.

The total peak current is limited only by the two series driver coils when the transistor is ON, if the self inductance of someone's coils is lower than that of Romero (about 2 x 1.2mH) or someone's switch ON time is longer than that of Romero used, then much higher current can flow via the Hall output and the base-emitter junction of the PNP so that heat can develope, either the Hall or the PNP transistor can get ruined as freenrgy850 reported the latter. Woopy somewhere wrote he already inserted a resistor as per the schematic below and he found current draw decreased, hence input power need also went down. But he used the original Romero circuit earlier without problem if I recall correctly.

Just noticed e2matrix also uploaded Groundloop nice schematic with a 10-20kOhm suggestion, it may prove to be too high in value nevertheless it can be tested.  This value greatly depends on the DC Beta (current amplification factor) of the PNP transistor (dI_c/dI_b).

Please understand:  the circuit as Romero showed without the resistor has been working for him without any problem and works for others too, I included the two main factors that may lead to overheating if exceeded.
For someone wishing to use FET driver ICs as manufacturer Application Notes show them or recommend them, it is also ok, mainly for long time operation, but for testing purposes Romero original circuit is just fine but you may wish to observe the recommandations above.

rgds,  Gyula

this one even better

[e2matrix]

Thanks much Gyula and Ron!  I've read every page here but no longer seem to have that photographic memory at all times      Thanks for posting the other values.   I'll repost my pic from GL to the correct values not that all the fuzziness is gone on this subject

Thanks Romero for chiming in again on this too. 

[baroutologos]

@ All above regarding Romero driving circuit,

To my view, it is a working circuit based on trial and error, that is not that intuitive for the average in the electronics neither it is as efficient as a FET circuit.

Have anyone noticed that transistor is wired backwards? In other words a PNP transistor would be expected to have the driver coils connected at its collector  and not emmiter. This way, coil resistance R (6 ohms + impedance) will limit the current going out of transistor's base to hall's FET

plus the fact that as the transistor switches on, less current would flow towards its base  (and hall consequently) and more will flow to collector since virtually no resistance there. In this topology, the transistor can never switch on completely.

Just try to see instead of coils place a light bulb (1 amp draw eg) and instead hall, put some 5-10 ohms resistance to ground.

[i_ron]

this one even better

hi romero,

Good to see your posts and note that your comfort level has gone up!

Wonderful new video too. However this has done nothing for my frustration level at all, lol

Wish I could see the number of connections on the coil and what the four transitor/FETs are doing? Oh well...

Warm regards,

Ron