Untill now I have been using DC loads to charge an ignition coil. However, I now want to work with a "magneto", a device that generates AC.
I have a specific switch in mind (have been using this with DC loads), however I wanted to ask; is it possible to convert two of these units into an AC switch, because obviously it would not let the negative current flow as is.
The switch:
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000023.pdf
Thanks.
I would say no because the unit can not stand a high reverse voltage from what I can tell from the data sheet. What you need is a triac or two SCRs.
Right, had a hunch that would be the case.
Oke, so lets say I had a triac like such:
http://www.produktinfo.conrad.com/datenblaetter/175000-199999/186414-da-01-en-TIC206.pdf
I would need an opto-coupler to power that, but how would I connect the pins on the triac, the names make no sense to me (MT1, MT2, G (Ground I assume)).
Thanks !
Edit:
Think I found a good component for the job:
The only thing I dont like about this, is that its turn on time states a MAX of 10ms, would that be possible ? since its just two triacs enclosed with a optocoupler ? or would this typically be a lot faster than 10ms, say 1ms ?
Lots of questions, hope someone can point me in the right direction.
G (Ground I assume)).
No it is the gate, it is where you put in the signal from the opto isolator.
MT1, MT2
Are the two terminals that get shorted together when the device turns on. Once on it stays on until the gate signal is removed and the voltage across it drops to zero or the voltage reverses.
is that its turn on time states a MAX of 10ms
No that is not a problem.
Thanks a lot for the advice!
I'm going to try my luck with a SSR, since I'm no vet, little ammount of self made components -> increased chance of succes.
blipinthedata:
Untill now I have been using DC loads to charge an ignition coil. However, I now want to work with a "magneto", a device that generates AC.I have a specific switch in mind (have been using this with DC loads), however I wanted to ask; is it possible to convert two of these units into an AC switch, because obviously it would not let the negative current flow as is.
Yes, you can connect two of those back-to-back in series. The snag is that you then need to provide a floating drive signal, assuming one side of the switch needs to be grounded (as is usual in the magnetos I have come across). One possibility is to drive them via a digital isolator such as ADUM6401, but that's quite an expensive option.
BTW that device is obsolete. The modern replacements appears to be IGBTs such as http://www.irf.com/product-info/datasheets/data/irgb14c40lpbf.pdf. Unlike the original device, if you wanted to connect them back-to-back in series, they would need to have parallel diodes connected to protect them from reverse voltage.
A triac or triac-based SSR won't do what you want. Magnetos generate ignition pulses by interrupting current, and you can't interrupt current using a triac.
I see, thats to bad then, already ordered a SSR haha. Ohwell, might come in handy someday anyway.
So my best option right now, would be connecting the two VB92ZFI mosfets back to back. Could you please elaborate on the "floating drive signal" ?
Thanks !
How about this setup, would this work:
The arrangements in the last two diagrams on that page are guaranteed to blow up the mosfets and possibly fuse the mains power supply, if the 230V AC in the diagram is a direct connection to the mains power supply. The principle shown in the first diagram is sound (because what it doesn't show is that mosfets have internal body diodes between source and drain). The problem is that 5V or 10V must be applied between the mosfet gate and source terminals, but the source terminals are themselves at a high voltage. So once again, you need isolated drive. An opto isolator can supply the isolation, but you still need a floating power source to provide the 5V or 10V, for example by feeding it through a transformer. The reason I suggested the ADUM6401 is that it provides both isolation and isolated 5V power.
I understand the problem now (i have a thick skull sometimes), thanks for sticking with it.
So the adum6400 actually isolates and also supplies the other side of the "isolation" with (nearly) the same voltage as you put in. That is indeed a fine component. I will post when I have ordered the parts and made a schematic, so that someone might check my idea.