Understanding electricity in the TPU.

[gyulasun]

...
A question I have is..........

Is there a mosfet that works in reverse and I don't mean the D and S going from positive to negative or from negative to positive. What I mean is when there is no pulse, the D and S are connected, instead of being non connected at no pulse. Like in a normal relay has N/O and N/C contacts, is there a mosfet that can have one or the other, or are all mosfets made to work the same way. Always N/O.
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Hi wattsup,

The MOSFET type you need is called depletion mode MOSFETs, they normally conduct at zero gate-source voltage. One of the manufacturers is ixys.com and see some type of them here:
http://www.ixys.com/Product_portfolio/products_link.asp?framepage=ixyspower_contact.htm&framepage1=http%3A%2F%2Fwww.ixyspower.com%2Fstore%2FFamily.aspx%3Fi%3D3

for instance a 200V device has 0.073 Ohm D-S resistance at zero volt gate-source voltage, see http://ixdev.ixys.com/DataSheet/DS100260%28IXTH-T16N20D2.pdf

However there are some power JFETs (junction FET) that conduct at zero gate-source voltage pretty nicely. Probably rather expensive, I do not know prices. 
An advantage with respect to the above depletion mode MOSFET is that jfets do not have any body diode between the drain-source whic is an unavoidable "blessing" for power MOSFETs.
See type SJDP120R085 from semisouth.com,  data sheet is here:
http://www.semisouth.com/products/uploads/DS_SJDP120R085_rev1.0.pdf

Fig. 8 in page 4 shows drain-source resistance between  -1V to +2V gate-source control voltage, at zero volt it has 0.068 Ohm resistance.

This is an N-channel type jfet, it needs a negative gate voltage wrt its source to switch it off. (Data sheet says this range is -6 to -4V.)

Probably there are some other makes from others, if you search key words 'normally on FET'.  But not many.

rgds, Gyula

[wattsup]

@gyulasun

Thanks for your post. It puts a good light at the end of the tunnel that I was considering today as being rather black and bleak. I will look up these components and see which ones are suitable for this type of switching requirements.

[wattsup]

Yes this makes perfect sense indeed.

P_Channel on positive side
Depletion Mode N-Channel on center
N_Channel on negative side

Tomorrow I will get some JFETs. Seems JFETs have been forgotten about by the  industry for quite a while. Wonder why? If they are normally closed, man oh man, thank you very much. Just wonder how fast I will be able to pulse them buggers and of course being true to the saga, how many I will toast before it works. lol

Added:
Interesting thread on JFETS.
http://www.designers-guide.org/Forum/YaBB.pl?num=1162476437/4

[wattsup]

Well, I got some small JFETs model NTE-132 and will use them with some small n-channel FETs I have model MPS3904.

I already tested the JFET with a dc going through the S and D then to my LEDS via 5 volts from my power supply. Then pulsed the gate at 1 hz and can see on the scope that in pulse off, the led lights up. Man oh man, we'z gonna have some more fun now.

I am looking for JFETs the size of my IRF840s but have not found any yet. lol

Also, since I will be trying this one on my bread board because this JFET is so small, I decided to start winding a test coil (photo below) more ready for this blotch wall movement. So I took a wooden ring and wound the first layer, all wound the same direction with opening at 180 degrees. One side will get the power, the other side will be switched. On this layer, I plan on winding one wind of my 1650 strand Litz wire. This will provide the most amount of copper sites to catch the blotch movement.

More soon.

[Mk1]

@all

I am sorry to say this but from what i see a blochwall can be done with a Joule thief circuit , take 5 min build one , one transistor one toroid and a 1k pot . Find the first schematic you see on google , all i see you doing is complicating stuff and use big batteries .

Just do it if you didn't already , you can build one with a secondary on top or one over a collector type coil pure tpu fashion , have fun .



In the real tpu most important thing it the vibration , something has to be moving now is it relays insulated spark gap , real movement or movement of energy .

If its real movement then is it like a motor or speaker ...

If you make a simple magnet motor 1 battery one magnet and one coil , and prevent the coil from rotating then you got a speaker , then remove the magnet and replace it by another coil Making it a 2 coil motor(no magnet ) , having a magnet in the proximity of the coils will generate movement ...

Think about it !!!

Now how come you can make a resonant circuit from a cap and a inductor , but not from two inductor you can if you wind them properly .