Testing the TK Tar Baby

[picowatt]

TK,

How goes the battle with the F43?

Have you attempted using a rechargeable battery with the Altoid's circuit?  After all, I believe all else was approved as being functionally similar to the NERD circuit, that is, that you would see the OU if only you were using a rechargeable battery.  No particular chemistry was dictated for that rechargeable battery.  Possibly it does not need to be a lead acid.

PW

[TinselKoala]

TK,

How goes the battle with the F43?

The F43 is checked out completely, and waiting for the output transistors to arrive from Singapore, the actual Motorola parts. The payment has been deducted from my bank account and the website says my order has processed and I will have a tracking number "soon". So it's just a matter of time for the transistors to arrive.  I have also ordered a couple more from someone on Ebay just in case, but they were twice as expensive.

Have you attempted using a rechargeable battery with the Altoid's circuit?  After all, I believe all else was approved as being functionally similar to the NERD circuit, that is, that you would see the OU if only you were using a rechargeable battery.  No particular chemistry was dictated for that rechargeable battery.  Possibly it does not need to be a lead acid.

PW

Well, all batteries are to a certain extent rechargeable. But.... the capacitor is sort of the "ultimate" rechargeable battery, isn't it? I mean, it stores its energy in the electric field between large metal surfaces, and the battery stores its energy in the electric field between tiny little ions in some chemicals....

But sure, OK. How about if I run it on a two-cell LiPo? I have a few of those around that aren't too important. And I can keep a bucket of water handy just in case.

How will I be able to tell if it's running longer than it should, though?

The really Really nice thing about the capacitor is that it is possible to charge it consistently to the same or nearly the same energy content for repeated testing. Batteries... well, as you have been saying, not so much. The LiPos are usually charged by an automatic charger -- but the only way to really tell how much charge is in a battery is to discharge it completely and measure what came out.

[Groundloop]

TK,

>>>But sure, OK. How about if I run it on a two-cell LiPo?
>>>I have a few of those around that aren't too important.
>>>And I can keep a bucket of water handy just in case.

Lithium and water is a dangerous mix. Never throw leaked
lithium batteries in water. Use a bucket of sand and transfer
the battery outside if it is leaking and smoking. If you have
nickel cadmium batteries then use them instead, much safer.

GL.

[picowatt]

The F43 is checked out completely, and waiting for the output transistors to arrive from Singapore, the actual Motorola parts. The payment has been deducted from my bank account and the website says my order has processed and I will have a tracking number "soon". So it's just a matter of time for the transistors to arrive.  I have also ordered a couple more from someone on Ebay just in case, but they were twice as expensive.Well, all batteries are to a certain extent rechargeable. But.... the capacitor is sort of the "ultimate" rechargeable battery, isn't it? I mean, it stores its energy in the electric field between large metal surfaces, and the battery stores its energy in the electric field between tiny little ions in some chemicals....

But sure, OK. How about if I run it on a two-cell LiPo? I have a few of those around that aren't too important. And I can keep a bucket of water handy just in case.

How will I be able to tell if it's running longer than it should, though?

The really Really nice thing about the capacitor is that it is possible to charge it consistently to the same or nearly the same energy content for repeated testing. Batteries... well, as you have been saying, not so much. The LiPos are usually charged by an automatic charger -- but the only way to really tell how much charge is in a battery is to discharge it completely and measure what came out.

TK,

I agree with the cap being the ultimate rechargeable, it is just that I thought "someone" said that you would see OU if only you were using a rechargeable battery.  Not sure if it was meant that it would demonstrate COP=infinity or something else. 

It is good to hear the F43 is only in need of outputs (if even that is "good").  Did you check the resistors around the pad switch to make sure none of them were toasted?

You might consider adding a bit more protection.  Since the pad circuit is at the output, I would want to protect that as well.  An inline fuse could be installed going to the output jack.  If you don't want to mod the unit, you could make up a cable with a fuse inline.  I would use a .750 to 1 amp fast blow.  Where distortion is a concern, the non-linear effects of an inline fuse can be reduced by bypassing the fuse with a cap (the resistance of a fuse varies with its temperature/load, similar to an incandescent).  For use with the TB, just adding the .75-1 amp inline will likely suffice.  Using a lower rating and having a few nuisance blows is better than toasted outputs.

Also, consider adding a pair of very fast diodes between the output and the output supply rails.  Anode of one diode to output, cathode to plus rail.  Second diode is cathode to output, anode to minus rail.  If any voltage is applied to the output that exceeds the output rails by a diode drop, the diodes will conduct and try to raise the rail (which is typically fairly low impedance).  The inline fuse will blow if the current draw exceeds the fuse rating during this condition.   If the pad circuit was in front of the output section and only a 50R between the amp and the output jack, I would use a fusable 50R and put the diodes at the amp out and sacrifice the 50R during an overvoltage.  But, as the F43 pad appears to be after the amp, I would protect the pad by placing the diodes at the pad output (at the output jack or wire thereto).

The reason for using fast or ultra-fast diodes is firstly they will conduct quickly when/if needed for protection and secondly they will have less capacitance to affect the output rise time.  For the least amount of rise time reduction, it is best to put the diodes right at the output of the amp section (ahead of the pad/50R).  But in your case, this could sacrifice the pad section during an overvoltage.  You may have to try the diodes at the output of the pad and see if they reduce rise time too much.  With very fast/low capacitance diodes you will probably be OK.

PW

 

[TinselKoala]

TK,

>>>But sure, OK. How about if I run it on a two-cell LiPo?
>>>I have a few of those around that aren't too important.
>>>And I can keep a bucket of water handy just in case.

Lithium and water is a dangerous mix. Never throw leaked
lithium batteries in water. Use a bucket of sand and transfer
the battery outside if it is leaking and smoking. If you have
nickel cadmium batteries then use them instead, much safer.

GL.

Thank you, that's good advice. I use LiPos a lot for my RC aircraft and other portable projects. If anything will make them explode, it will be this circuit !

NiCads are not as much fun. What about NiMH? But I have more LiPos than anything else. Of course, when they don't work, then that will just mean that LiPos don't work. Then when the NiCads don't work.... well, you know. It will turn out that only RayLite Silver Calcium LA batteries manufactured in the Southern Hemisphere will work. Or will they?

You do realise that you are RA's hero experimenter, don't you? I hope that you are having all the fun you can handle.