Clock battery using "in stock stuff"

[silence dogood]

Using a zener diode of that voltage to limit the voltage would be the crowbar effect. the battery would die fast.

We did that once back in the CB days.

Held the voltage fine, but the power supply did not like it.

One could use it in bias to the transistor to set the voltage, but now it gets complicated and has idle current.

Our circuit draws no current when idle, reduces the contact current to less than 1 mA, then provides the correct current AFTER the switch has made contact.

It also limits the current to a similar amount to protect from shorting wires or coils.

And only 3 active parts.

We added accessory items such as a set of banana plugs in series with the battery to allow easy current measurement.

We could have just got some battery holders and used D batteries like most, but they did not have them.

One coukd claim over-kill, considering only 3 parts and the function it seems otherwise.

Using a PLU to same would be that.

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You are right. I was just being facetious. Considering all the other factors in the total circuit, I consider your circuit ideal. Simple and effective.

 

[tq60]

We guessed that, all in fun!

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[silence dogood]

Thanks, tq60. Thought maybe my little humor fell flat. Now for a little explanation on not using a Zener diode. If a voltage is over a certain level, the Zener will basically short out, causing a voltage drop. This is why the circuit is called a "crowbar" or in this case a clamping circuit. When the voltage reaches a certain level determined by the Zener, the Zener will turn off. To smooth out this on/off cycle, you add a capacitor. The problem with this circuit it that in order for it to work, it has to draw more current in addition to the load current. Tq60's circuit is very elegant not just because of its simplicity but also it is very efficient. Using a germanium transistor is brilliant. Germanium transistors are more efficient than silicone, hence much less current draw.

 

[tq60]

Actually, due to basic Ohm's law, it is 100 % efficient.

All components as a group, end up as a series path, so any and all currents flow through the clock coils.

Acts as an automatic self adjusting series pot.

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[tq60]

Although I use Li ion batteries most of us rc airplane guys are Lipo users and are maniacs with charging and monitoring.

One of the batteries we used was bad. It would self discharge and take out the other one.

They also were bare cells. The support circuitry was on a flex.

We also did some research on charging, and trickle charging is not good.

Found some similar sized batteries for about $14.00 each, 3800 mA. With built-in support circuit and JST connector.

Also found a wall wart style lithium charger that fit the connector we used, removed the resistor, and it works well.

We designed and built using stuff we had, but we bought new batteries and the correct charger. Do it right.

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