Driving a JFET from a micro

[6666]

Good experiments Ivconic

[dbanner]

I think there needs to be an intermediate drive circuit between the micro and ordinary power mosfet for voltage level. I was looking at the Cscope schematic at the beginning of the thread and comparing it to the HH2 tx drive circuit.

[ivconic]

I think there needs to be an intermediate drive circuit between the micro and ordinary power mosfet for voltage level. I was looking at the Cscope schematic at the beginning of the thread and comparing it to the HH2 tx drive circuit.

Yes it is.
Take original Barracuda, pull out CD40106 and attach Arduino UNO with wires on its place, it will work just fine.
I did that in the past. Checked.
With notice; GND from Arduino goes to Barra's -5v and +5v from Arduino goes to Barra's GND.
You don't need to change anything else on original Barracuda pcb. It will work fine.
I am trying something bit different here. To include Atmega, 2-stage RX and 4053 switching on the same pcb.
So some changes must be done. Half success so far. It works, not having good "depths".
Probably bad timing.

[Carl-NC]

I think there needs to be an intermediate drive circuit between the micro and ordinary power mosfet for voltage level. I was looking at the Cscope schematic at the beginning of the thread and comparing it to the HH2 tx drive circuit.

For the TX FET, I now mostly used a SPDT analog switch, such as 1/3rd of a 4053. Many of the MOSFETs like to have a high drive level (maybe 10V) and having very low impedance drives is a plus for both turn-on and turn-off. And the 4053 can be driven from 3V logic.

[dbanner]

I've been opening up lots of old phone charges just because I have a lot of them lying about the place useless.
Now I've noticed that most of them contain optocouplers. 4 pin jobs, anode,cathode,emitter, collector.
I was wondering if these could be used to drive the mosfet from the pulse provided by the micro.
Here is the datasheet for one from a typical phone charger. Perhaps two could be arranged in totem pole configuration.
The idea is to experiment with otherwise useless components which can only be put in the garbage pale.

[dbanner]

I've been opening up lots of old phone charges just because I have a lot of them lying about the place useless.
Now I've noticed that most of them contain optocouplers. 4 pin jobs, anode,cathode,emitter, collector.
I was wondering if these could be used to drive the mosfet from the pulse provided by the micro.
Here is the datasheet for one from a typical phone charger. Perhaps two could be arranged in totem pole configuration.
The idea is to experiment with otherwise useless components which can only be put in the garbage pale.
Maybe the transients are not suitable on this one.

[dbanner]

Another possible use is to drive a VC0 circuit for audio.

[Cazavor]

I've been tearing down old PSUs and salvaging components as well. The optocouplers I've found so far are the JC817 like yours, 4N35 and PC123. What they all have in common are rise/fall times and propagation delays in the microseconds range. For example the 3 μs typical 18 μs max fall time on the JC817. Surely too slow for controlling sampling or driving the TX?

[dbanner]

I've been tearing down old PSUs and salvaging components as well. The optocouplers I've found so far are the JC817 like yours, 4N35 and PC123. What they all have in common are rise/fall times and propagation delays in the microseconds range. For example the 3 μs typical 18 μs max fall time on the JC817. Surely too slow for controlling sampling or driving the TX?

Yes, that's what I meant by the "transients" not being good.

[dbanner]

There are however high speed optocouplers, like the 6N137A which boasts of rise and fall times in the tens of nanoseconds range. Surely these are fast enough to do the business.

[dbanner]

Here is a document which describe a means of improving the rise and fall times of optocouplers by cascode method, which I think can be used to implement a faster VCO response with these general purpose optocouplers. Maybe of interest.

[ivconic]

Yes it is.
Take original Barracuda, pull out CD40106 and attach Arduino UNO with wires on its place, it will work just fine.
I did that in the past. Checked.
With notice; GND from Arduino goes to Barra's -5v and +5v from Arduino goes to Barra's GND.
You don't need to change anything else on original Barracuda pcb. It will work fine.
I am trying something bit different here. To include Atmega, 2-stage RX and 4053 switching on the same pcb.
So some changes must be done. Half success so far. It works, not having good "depths".
Probably bad timing.

I checked this again, just to be sure.
It works slightly BETTER than with CD40106.
And much more cleaner!
Watch the new video i just posted here:

https://www.geotech1.com/forums/show...136#post269136

[Cazavor]

There are however high speed optocouplers, like the 6N137A which boasts of rise and fall times in the tens of nanoseconds range. Surely these are fast enough to do the business.

6N137A looks good, but the 5.5 V max recommended supply voltage needs consideration, especially with mosfet circuits that like higher voltages.

[Altra]

I tried the TLP250 and they worked as well as the FOD3180/ IX3180, but minimum supply voltage is 10V. The datasheet says they are used in air condition and heating systems which means you might find some in the junk pile?

https://www.google.com/search?sxsrf=...w=1280&bih=604

[dbanner]

I tried the TLP250 and they worked as well as the FOD3180/ IX3180, but minimum supply voltage is 10V. The datasheet says they are used in air condition and heating systems which means you might find some in the junk pile?

https://www.google.com/search?sxsrf=...w=1280&bih=604

Well I do have some controller boards from air conditioning in the junkbox. I'll have a look.