Branch's SSG Build

[BobZilla]

You know what else is interesting is that I'm hearing a chorus effect coming from the SG now. I'm speaking from an audio standpoint...when you hear two audio signals phasing in and out of each other...and it sounds like a watery chorus effect. It's a little discerning haha.

Yup I hear that on mine too if I listen closely. I have found that good charging occurs if you loosen resistance just a tad, I mean a very little bit once you hear that. Very hard to describe but now you know what i man when i am always saying I can just hear when things are in tune. On my setup I can hear it without external gear but that may just be my hearing range or the machines could be different but regardless I know what you mean about the chorus.

Also your recorded tracks sound pretty similar to what I hear on my machine. Mine has larger wire and two coils so of course it will be a little different but basically the same. And you are right in that the very slightest change on resistance does have a drastic effect, now you have figured out a way to monitor using an audible indicator. Setp a timing light with an led and it will all paint a bigger picture for you. Don't leave a timing light on during the run, just spot check with it. It will draw power from the circuit so you don't want it connected any longer than to just take a quick look at what is going on. You can use two led's like I have with different colors and see both the coil charge and release. Just connect them in opposite directions, one lights while other doesn't and then they reverse.

[Branch Gordon]

Those LEDs....are those just connected to the top and bottom of the trigger coil?

Yup I hear that on mine too if I listen closely. I have found that good charging occurs if you loosen resistance just a tad, I mean a very little bit once you hear that. Very hard to describe but now you know what i man when i am always saying I can just hear when things are in tune. On my setup I can hear it without external gear but that may just be my hearing range or the machines could be different but regardless I know what you mean about the chorus.

Also your recorded tracks sound pretty similar to what I hear on my machine. Mine has larger wire and two coils so of course it will be a little different but basically the same. And you are right in that the very slightest change on resistance does have a drastic effect, now you have figured out a way to monitor using an audible indicator. Setp a timing light with an led and it will all paint a bigger picture for you. Don't leave a timing light on during the run, just spot check with it. It will draw power from the circuit so you don't want it connected any longer than to just take a quick look at what is going on. You can use two led's like I have with different colors and see both the coil charge and release. Just connect them in opposite directions, one lights while other doesn't and then they reverse.

[Tom C]

aaah resonance !!
Tom C

[John_Koorn]

Those LEDs....are those just connected to the top and bottom of the trigger coil?

Very interesting Branch

The timing light goes across the power coil wires - or emitter buss and a transistor collector.

John K.

[BobZilla]

Oh Branch make sure and put resistors on the timing lights, otherwise you will probably blow them. I am using the big square kind so I have less resistance on mine but for normal round type put around 300ohm or so....


Also here is a little hint for tuning... I'm not going to say how to set things up because it is all a matter of opinion but once you have a timing light you can also use it to check the machines natural induction. What do I mean by that..... you can go across your trigger coil or power coil, heck check both but anyway with the led hooked up and the machine up to speed,, turn off the machine and watch the led, not the timing mark we are not checking timing with this procedure, watch the Led itself. It will be a good indicator of the magnet induction that is happening across the coils. This will have everything to do with your coil gap.

[Branch Gordon]

Hmm....I will be hooking it up tonight to check it out. I wish I understood what to look for with the LED, relating to induction. Maybe it will become apparent as I watch it.

I will add resistors to my LEDs too, thank you!

Oh Branch make sure and put resistors on the timing lights, otherwise you will probably blow them. I am using the big square kind so I have less resistance on mine but for normal round type put around 300ohm or so....


Also here is a little hint for tuning... I'm not going to say how to set things up because it is all a matter of opinion but once you have a timing light you can also use it to check the machines natural induction. What do I mean by that..... you can go across your trigger coil or power coil, heck check both but anyway with the led hooked up and the machine up to speed,, turn off the machine and watch the led, not the timing mark we are not checking timing with this procedure, watch the Led itself. It will be a good indicator of the magnet induction that is happening across the coils. This will have everything to do with your coil gap.

[Branch Gordon]

In regards to base resistors, I am not sure I totally understand how they work in the SG circuit. Currently I have 470 ohm resistors soldered in place, and I have the master resistance at 50 ohms.

So if I were to replace the base resistors with 100 ohm resistors, then would the same master resistance be 50+370 to compensate for what I lost in the base resistance?

[Tom C]

https://learn.sparkfun.com/tutorials...llel-resistors

learnin how to fish


Tom C

[ErikN]

In regards to base resistors, I am not sure I totally understand how they work in the SG circuit. Currently I have 470 ohm resistors soldered in place, and I have the master resistance at 50 ohms.

So if I were to replace the base resistors with 100 ohm resistors, then would the same master resistance be 50+370 to compensate for what I lost in the base resistance?

Hi Branch,

Your assumption is correct if you have a single transistor. However, multiple parallel transistors complicates things.

If one assumes Vbe is identical for all four parallel transistors, the base resistors can be considered in parallel. 50 + ( 470 || 470 || 470 || 470) = 50 + 117.5 = 167.5 ohms

To get the equivalent resistance with the base resistors at 100 ohms, you have X + (100 || 100 || 100 || 100) = 167.5 or X = 167.5 - (100 || 100 || 100 || 100) = 167.5-25 = 142.5 for a new master resistance.

Hope that helps!
Erik

[Branch Gordon]

Oh ok I have assumed this whole time that the master resistor was in series to the base resistor.

So there is slightly more lower resistance tuning available if you go with a lower base resistance, if I am understanding correctly...

Why is it recommended then to start with 470 ohm resistors, if you can get more tuning range from 100 ohm and 1k pot?
Is this just to get everyone on the same page for their first build?

Hi Branch,

Your assumption is correct if you have a single transistor. However, multiple parallel transistors complicates things.

If one assumes Vbe is identical for all four parallel transistors, the base resistors can be considered in parallel. 50 + ( 470 || 470 || 470 || 470) = 50 + 117.5 = 167.5 ohms

To get the equivalent resistance with the base resistors at 100 ohms, you have X + (100 || 100 || 100 || 100) = 167.5 or X = 167.5 - (100 || 100 || 100 || 100) = 167.5-25 = 142.5 for a new master resistance.

Hope that helps!
Erik

[Branch Gordon]

Thank Tom for the link. I do understand series vs parallel resistors...I am more interested in what motivates the choice of a particular base resistor on a build vs another.

https://learn.sparkfun.com/tutorials...llel-resistors

learnin how to fish


Tom C

[Tom C]

JB designed the circuit and that is the resistor he chose for the right amount of current for the base of the transistor, all things being equal.

Tom C

[Branch Gordon]

Tom,

I'm trying to drill down for something more specific here. I understand that John B. designed the circuit...I also understand he chose a 470 ohm resistor on his SG.

Why? I have run my SG at 220 ohms and 470 ohms, and it stays cool both ways...and I can achieve the same overall resistance either way. There must be a technical reason...beyond just that "that's the way it is". I'm trying to understand concepts here man...maybe they are dumb questions...I don't know...but that's what this forum is here for.

JB designed the circuit and that is the resistor he chose for the right amount of current for the base of the transistor, all things being equal.

Tom C

[Tom C]

its not about temp per se... although extremely low resistance will shove the base on and pass current which you don't want. there is a performance curve for the transistor..... at a given resistance for a given type of magnet for a specific type of core the induced current in the trigger winding is correct to switch the transistor on fully but not on for too long. 470 or 680 ohms. as you reduce base resistance the base stays on longer, causing more current from the primary. you only want the spike, which is the start of the h the rest is battery current not potential. base on too long and the batteries are just connected pos/pos and neg/neg. base not on long enough and you get multiple lower voltage spikes as the transistor oscillates off and on. you want 1 spike, and with most setups 470 will give you one spike. that is the long way of saying it

Tom C

[BobZilla]

Yup I agree with what Tom is saying so don't take what I am about to say as a contradiction, he is explaining it exactly as it is.

Anyone watching my new machine thread knows I have been playing around with 2 spike, one spike, three spike to see the differences. When we setup for one spike it seems to me that that is the true spike produced from the induction triggering mechanism. When we get more spikes I think it is the circuit going into self oscillation for a brief time , probably the power winding inducting across the trigger and re-opening the base.

For me a question has been if two spikes could be better, I am not saying they are but just thinking out loud about it. One side of reasoning is that you double the frequency, yes smaller voltage but double the amount of them. I have no way to see the actual spikes to look for the spike potential and that is where it is all at as Tom has said.

In my experiment I am assuming that although 2 spikes has lower voltage the two of them may add up to more harvesting than the one larger one but do not know really for sure, it is an assumption. I am really not putting fourth an assertion that one is better than two or two better than one, just trying to think it through. I know that my machine will charge both ways and I did some runs in my thread to support that.

I shot a video of what I am talking about. I did not really explain all to well in the video what the point is but it shows me running the machine with one spike and two, while looking at the AC frequency across a power coil and also the voltage the meter senses. Again most of this is based on assumption that may not be accurate to what is really happening, these are just honest observations and hypothesis. The actual spike we are all interested is not even represented because I don't have the equipment to monitor it, all I can do is monitor by-products around it.

Here is the video:
https://files.secureserver.net/0s8o4eviuBnWwE