Square Wave using 25Mhz Crystal oscillator

[Farmhand]

Yeah Mark, I was actually talking about two different circuits there, my bad I did not explain myself well at all.

Circuit 1) with the SG3525 was a suggestion for a chip which with a simple circuit can run up to 100 Khz or so and take 30 volts or more.

Circuit 2) Is an oscillator I made from a CD4001 chip and can run up to over 5 Mhz, but the driver chip I have for the mosfets gets hot on that one over 1 Mhz and I see a lot of ringing on the top of the signal waveform, like a resonant ripple, a poorly designed circuit for those frequencies for sure. Just saying at higher frequencies requirements for driving the switches gets more complicated. I only required 900 Khz so I did ok with it for some experiments.

I make boards for different experiments, but I make them so they can be reused easy for other experiments. One board I don't have is a H bridge board. 

Cheers

[TheOne]

To make a square wave you need a transistor that when it turns on will pull the output up to a voltage, and for the falling edge a transistor that when it turns on will pull down the voltage.  It is important that both transistors do not conduct at the same time.  If they were to do that, then they would present a short circuit across the power supply which would be hard on the transistors and very wasteful.  Devices like the ICs I suggested impose a little delay, IE dead time between when they turn off one transistor, and when they turn the other transistor on to prevent simultaneous conduction and the resulting destructive shoot-through current.

If you have a two winding coil operating in a push-pull configuration, then when one transistor turns on, the other transistor's collector (bipolar) or drain (MOSFET) will fly up to twice Vcc.  When one of the transistors / MOSFETs turns off, then the voltage at the transistor turning off rises up and the voltage at the off transistor falls down until the magnetizing current in the coil finds a discharge path.  If you turn on both transistors at the same time then the magnetizing flux in each of the two coils cancel and the current through each coil builds-up very quickly to destructive levels.

The bottom line:  Never turn both transistors on at the same time.  Make sure that you insert enough dead time between when you turn the on transistor off and the off transistor on so that they do not both conduct at the same time.

1MHz would be fast for most MEG constructions that I have seen.

This unit for $65.00 will make pulses up to 40MHz for you:  http://www.ebay.com/itm/40MHZ-DDS-FUNCTION-SIGNAL-GENERATOR-DIY-KIT-SPI-I2C-MASTER-SLAVE-PULSE-GENERATOR-/261383840015?pt=LH_DefaultDomain_0&hash=item3cdbb0e10f

Yeah it would be fast but none of the MEG I have seen use magnetite as core, maybe I can go over 1Mhz.


I buy some magnetite recently from washington, I will not use any epoxy or glue in it, I want to print a 3d case in transparent plastic, I ordered a cheap 3d printer, but they ship in april , so I have plenty of time to work on the circuit http://store.qu-bd.com/product.php?id_product=145


Thank you for the link

[TheOne]

I think i find a cheap signal generator that will probably do the job http://www.aliexpress.com/item/Cheap-AD9850-DDS-Signal-Generator-Module-Free-Shipping-TK0459/837129360.html


The only down side is they are no screen


or this one with a screen http://www.aliexpress.com/item/Free-shipping-New-DDS-Function-Signal-Generator-Module-Sine-Square-Sawtooth-Triangle-Wave/715787982.html
http://www.aliexpress.com/item/Free-shipping-0-30MHz-DDS-VFO-electronic-Signal-Generator-based-on-AD9850-Direct-Digital-Synthesis-HAM/932970027.html

[mscoffman]

Make sure you review capacitor bypassing for the Vcc of all digital devices in this service. This is especially
true when one has spikes from power inductors and/or shoot through. There nothing better then seeing
an IC flip-flop sitting there flipping all by itself with no clock inputs to convince one that there is a need for better
digital power supply/ground distribution. Digital circuits are actually a good training review for overunity systems
generally. You'll need find a special path for those dark currents.

Also please let us know if find anything interesting with your MEG.

[TheOne]

Make sure you review capacitor bypassing for the Vcc of all digital devices in this service. This is especially
true when one has spikes from power inductors and/or shoot through. There nothing better then seeing
an IC flip-flop sitting there flipping all by itself with no clock inputs to convince one that there is a need for better
digital power supply/ground distribution. Digital circuits are actually a good training review for overunity systems
generally. You'll need find a special path for those dark currents.

Also please let us know if find anything interesting with your MEG.

Yes, I actually started another thread but I was asking help for circuit.


I will update over time, my primary objective with the MEG is to power-up the circuit with only the input coils once the circuit is running from a 9volt battery and later [size=78%]add 4 others output coils later to power-up load...[/size]