Circuit setups for pulse motors

[tropes]

Okay Champ. Could you upload a bitmap of a safer circuit with a PNP transistor.
Happy motoring
Tropes

[Ren]

tropes, effectively it should be the same as this one hoptoad has posted.

http://www.totallyamped.net/adams/index.html

Note the resistor placed in diagrams between positive of battery and hall positive input. Dont change anything else on your current wiring schematic as of yet. By the way what are the voltage ratings of the hall your are using?

Hoptoad, am I correct in placing a diode between base and emmiter (allowing flow from base -> emmiter) in a pnp application? How can I figure out the best diode for this application? And do you need to protect the output from the hall? Thaelins post earlier on mentioned something about that although I could have misread him.

[hoptoad]

toad you are the man. Required reading for anyone using halls above. Oh yeah, go the milo. 5 parts milo to 1 part milk, its the only way

Tropes, my basic understanding is that a pnp and an npn are very similar, the only difference is the way the current flows, hence connections. In our pnp setup you would hook the firing coil up to the emmiter, as opposed to a npn where you would hook it up to the collector. Look at the link I posted in the other thread regarding pnp and npn, and anyone please correct me if I am wrong.

So hoptoad, could I place a variable resistor between + and the input to hall to limit current flow to hall? Will this have any effect on switching time/duration? By that I mean can I vary the resistance to the hall to vary the on/off time, much like you would do with a pick up coil (see Bedini setup)? Or would just a simple resistor be more suitable. My halls are 3-30 v rated. Thanks again champ.

Hi Ren - I can't stay long, I've got some deadlines to meet re: work. Yes you can use a variable resistor. I would recommend putting a fixed resistor of say 100 - 200 ohms in series with a 1000 ohm Pot. That way, if you accidentally wind the pot back to 0 ohms, you will still have some fixed amount of protective resistance in the circuit. Also whether using a PNP or NPN arrangement, it is still recommended that you put your drive coil on the Collector side rather than the Emitter side, to fully isolate the control and driving current paths from each other. I only ever had easy access to a single version of Hall which was designed for NPN bias type connections, but if you can get a Hall with PNP bias characteristics, then essentialy as you've said, the circuit layout would be the same as I have shown on my site, but polarities are simply reversed.

Also putting a diode in reverse bias across the base to emitter junction will assist slightly in arresting reverse voltage spikes in the control circuit. Do not put the diode in forward bias mode across the junction, as this will then always limit the bias voltage to the base of the transistor to the value of the voltage drop across the diode. For Silicon diodes this will be .6 Volts and for Germanium it will be approx .4 V . Will address some more of these issues when I get the chance, and will continue to post on my site more sophisiticated (but still simple) versions of NPN switching circuits when I get the chance.

Cheers for now. 

[tropes]

tropes, effectively it should be the same as this one hoptoad has posted.

http://www.totallyamped.net/adams/index.html

Note the resistor placed in diagrams between positive of battery and hall positive input. Dont change anything else on your current wiring schematic as of yet. By the way what are the voltage ratings of the hall your are using?

Hoptoad, am I correct in placing a diode between base and emmiter (allowing flow from base -> emmiter) in a pnp application? How can I figure out the best diode for this application? And do you need to protect the output from the hall? Thaelins post earlier on mentioned something about that although I could have misread him.

Ren
To answer your question the supply voltage range of the unipolar Allegro 3240Ua Hall IC is 4.2-24 volts. I have used several other bipolar Hall IC's with similar ratings.
Now have you been to
http://www.theowlnest.com/circuit.html ?
What I have requested is to have a bitmap from Toad which can be uploaded to this site. All other information and instructions I appreciate and understand. I have also placed a 1N4007 diode between the collector and emitter of the transistor.
If a bitmap ( jpeg. or gif.) cannot be uploaded just say so and I will understand.
Peter

[Ren]

oh.. ok sorry . Yes that will be a handy page for us to refer too, as well as others who may come.

Thanks hoptoad for the info. Let me see if I get this straight. I can hookup my pnp circuit with the coil connected to the collector and then run the emmiter to the ground? It will work the same way but with the benefits of isolation and capture on the collector? Or should I just get a npn?

Im off for a small holiday guys, look forward to catching up in a few days.

Take care.