calculating proper base resistors

[LesK]

Ok, I finally made it here, so I wanted to cover a basic area of the SSG.
JB has said many times you have to design the coil to match the voltage you are going to run at.
So far as I understand, a 24 volt coil is 1.2 ohms #18 awg. If this is correct then the next step in designing the coil would be to determine
the base resistances used. I have been just using 470 ohm resistors. But I got to thinking about Ralph's machine. I realized we knew almost everything about it.
Even that it was tested at 12 volts not 24. So I was wondering what his base resistors were and maybe some ideas on how to determine what would be a good process
for calculating for any build we may want.

Thanks
Les

[trancedrum]

Hi Les,
Base resistors 56 Ohms
Branch resistors 22 Ohms
Light bulb + 12 Ohms (trigger) so total 90 Ohms
JB I think suggested 64 Ohms (base + branch) so I have a little to much.
Thanks
Ralph

[Ren]

I would love to hear peoples thoughts on the branch or balance resistors used between boards. Specifically, what is their purpose, and how does it improve the machines operation over a circuit without?

Are they necessary if all circuits are soldered directly to the common bus (I have a 3 coil, 18 transistor build using the PCB's all strung together in a line) or is it not about physical layout of the circuit and more about accomodating each coil? By that I mean, are the branch resistors there because the circuits for each coil are mounted separate from each other, or is it more than that? Do we benefit by placing a lower resistance directly on the base with branch resistors making up the difference as opposed to just "averaging" the branch resistance across all bases (higher base resistances all round)?

Im sure John has them there for a specific purpose, I have just never seen it talked about much, beyond a simple one liner like "to balance the trigger currents out" or such. If its as simple as this, fine, but is there more to it?

Regards.

(Love that machine of yours Ralph BTW)

[LesK]

Thank you Ralph,

I guess I must not have a correct SSG schematic. I have always been using the hand drawn version that only shows one 22 ohm resistor on the trigger coil, and then one 470 ohm for each base. So Where are the branch resistors vs base? Or is there a schematic posted somewhere I have missed?

Les

[Ronnie]

If I have been paying attention, I understand that it has been said that on the 10 coil machine like JB setup, you are running 24v @ 1amp/coil or240+/- watts. If this is true?? Then it would seem to me that you would set your total resistance to achieve this goal.
Having branch resistors to me spreads out the work load, so that not all your amps are going through just one resistor. just my opinion.

Have a great day
Ronnie

[Tom C]

Thank you Ralph,

I guess I must not have a correct SSG schematic. I have always been using the hand drawn version that only shows one 22 ohm resistor on the trigger coil, and then one 470 ohm for each base. So Where are the branch resistors vs base? Or is there a schematic posted somewhere I have missed?

Les

the vanilla SG has 100 ohms on the base then a pot, for figuring fixed resistance. this is where tuning comes in, it all depends on the final set up. my 8 filar has 22 ohms on each base and a final resistor of 470 ohms. that is where it runs best. I have discovered that all circuits are drawn in the context of what is being driven, often times we dont know what is being charged. I do know that the bike wheel jb has charges the heck out of pretty much whatever he attaches to it.

Tom C

[alfinip2000]

Ralph, did you beta match the trans, diode and check the ohm of the coil? Nice set up you have there

[LesK]

Basic slave circuit

Ok, do these changes correctly represent Ralph's machine?




Thanks
Les

[min2oly]

Hi Les,
I thought the branch resistors go before the base resistors rather than before the power coil as they appear in that picture?
Kind of like AT the fork in the road where, if you follow the prongs, they lead to the base resistors and on to the base of each transistor?

nice thread, I'm glad we are all getting to the nitty gritty of all these components and tuning etc...
Kind regards,
Patrick

[Ren]

I was under the impression branch resistors referred to only multicoil builds, specifically the resistors used to connect the trigger to each board. I always saw the above schematic as having base resistors and a master resistance, usually coupled with the lamp, or essentially where the pot goes for us noob's =)

The branch resistor is something I only noticed on Johns multi coiler pics and when Ricks PCB surfaced. One needs not use it if one only uses one board, or so I thought.

Be good to define all terms used exactly I guess, so there is no confusion.

Regards

[RS_]

Hello all,

As my first post on the new forum, I think this is a good subject, as I built muilty strand and muilty coil SSG's, before anyone else even knew about them.

The base resistors need branching out so that none of the transistors, or group of 4 transistors can not hog all the trigger current for what ever reason.

On my 48 strand 6 coil SSG, I have a Matched set of 22ohm resistors on each base, then for every 4 transistors, I have a matched set of 47ohm resistors, that feed the 4 22ohm resistors, then for every 16 Transistors, I have 2 matched 47ohm in parallel for 23.5 ohms, and a higher total wattage rating for that set that feed the 4 47ohm and then the 16 22ohm. Then there is the Lamp, that is in parallel with some resistors, or a high wattage Pot depending on how i am tuning it that feed the 3 sets of parallel 47ohm.
Chad and I also matched all 48 base Diodes voltage drop. We only tested the beta on a sample of 10 of the MJL transistors, as they were all exactly the same, we did not bother to test all 48. We also matched the voltage drop on the 48 output Diodes.

Branching/dividing the trigger current like this through a Matched Resistor Network, and matching the diode voltage drop, Forces all the transistors to operate exactly the same.

Hopes this helps understand what the Resistor branching does.....

RS

[min2oly]

RS, thanks for the post.
what watt rating did you use for the base resisters VS each of the Branch?
should we be using a high watt rating for all. or should we be limiting in some way?
Thanks,
Patrick

[RS_]

branch resistor watts

RS, thanks for the post.
what watt rating did you use for the base resisters VS each of the Branch?
should we be using a high watt rating for all. or should we be limiting in some way?
Thanks,
Patrick

I used 1/2 watt on the 22ohm and the 47ohm... but the 47ohm needed to be 1 watt, as the 1/2 watt resistors are turning brown, the 2 parallel 47ohm should be 1 watt resistors, or 1 22ohm at 5 watts

[LesK]

Ok RS,
Good to see you here, and thank you for this insight. It never made sense to me to add a resistor in series with the coil. This would seem to also apply to the half bipolar where we are using multiple parallel transistors on the Ferris Wheel.
Which makes me wonder why we don't have a group here for it as well....?

Thanks
Les

[RS_]

Les and all,

I hope JB does not mind if I post this Muilty Strand SSG Sch showing the Branching resistor divider network, as it is based on his advice..........
I also think that the muilty transistor Bedini/Cole driver could benefit from some 10 to 22ohm base resistors