Testing the TK Tar Baby

[fuzzytomcat]

Here is the schematic for "Manny" the manual mosfet relay driver/oscillator, so far, as developed and demonstrated in the last several videos. I am really lousy at schematic layout; it is really not as complicated as it looks. I hope I've drawn it out correctly, at least.

I hope it is clear to the readers what I am doing here.

By using a double-pole double throw relay and the correct reservoir capacitor and charging-discharging trimpots, one can use this circuit to control another circuit that requires alternate application of voltages at long arbitrary duty cycles.

In other words, I have again implemented one of the suggested means of driving the NERD circuit without the use of an expensive and delicate FG or even a mysterious 555 timer, to produce both the Q1 ON high heat mode and the Q2 magic oscillation modes of operation, with virtually any duty cycle desired, for about 12 dollars in parts. That is, I am still doing the NERD "team's" homework for them and publishing it freely as it happens.

Hi TK,

The relay your showing as a SPDT is that correct ? Most have c-face (common) NO NC contacts .... I could be wrong though 

Fuzzy

[TinselKoala]

Hi TK,

The relay your showing as a SPDT is that correct ? Most have c-face (common) NO NC contacts .... I could be wrong though 

Fuzzy

Yes, the relay that is controlling the charge, discharge cycle is SPDT, with the NO contact the discharge and the NC contact the charge. I know this makes the relay coil active most of the time and "off" in very short bursts as the cap charges quickly, and that wastes power, but it is the simplest way to do it. If I were building this for an application I'd invert the signal to the relay coil with a 2n2222a and swap the ch-disch contacts around; that way the relay coil would be OFF most of the time and save power.
I may try that anyway on the board if there is room.

ETA: I meant that to control the NERD circuit, you'd put another relay in with a DPDT contact set, or use a TPDT relay in the first place, with one pole doing the feedback switching and the other two controlling the NERD circuit.

Like this:

[fuzzytomcat]

Yes, the relay that is controlling the charge, discharge cycle is SPDT, with the NO contact the discharge and the NC contact the charge. I know this makes the relay coil active most of the time and "off" in very short bursts as the cap charges quickly, and that wastes power, but it is the simplest way to do it. If I were building this for an application I'd invert the signal to the relay coil with a 2n2222a and swap the ch-disch contacts around; that way the relay coil would be OFF most of the time and save power.
I may try that anyway on the board if there is room.

ETA: I meant that to control the NERD circuit, you'd put another relay in with a DPDT contact set, or use a TPDT relay in the first place, with one pole doing the feedback switching and the other two controlling the NERD circuit.

Like this:

I took the liberties to modify your schematic to what I think you are doing ..... it's early and I need more coffee 

[TinselKoala]

Using the output from a power mosfet to switch a 2n2222a is not the silliest thing I've thought of today, but it's close. I'll see if I can get it to work just for the lulz.

[TinselKoala]

I took the liberties to modify your schematic to what I think you are doing ..... it's early and I need more coffee 

Not quite, but almost.

The C or movable contact of the relay is connected to the 33 uf Cap, and the NC contact is connected to the charging trimpot. In other words, you have the head of the arrow on the wrong end of the line.

Sorry I'm such a lousy sketcher.

Have another cup of coffee, on me.