SciKidsMom
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BREADBOARD w battery pack sub for regulated power supply

Postby SciKidsMom » Sun Feb 28, 2010 1:03 am

batteries not included...

Materials list for Linear or Logarithmic project plus a few other circuits call for a "solderless breadboard with regulated power supply (+/-5 V, +/-15 V)". No power is available or allowed. Need to be sure adaptation for battery powered solderless breadboard is correct.

How critical is the placement of battery pack wires into breadboard as long as positive is on the power bus side and negative is on the ground side?

How can battery packs best match +/-5 V, +/-15 V?

(i.e. will a 6V AA pack work for 5V? 6 + 5 = 15 but does 6V + 5V = 15V?)

rmarz
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Re: BREADBOARD w battery pack sub for regulated power supply

Postby rmarz » Sun Feb 28, 2010 2:03 pm

SciKidsMom - Many generic breadboards want to support digital logic such as 7400 bipolar or CMOS logic types typically requiring a single 5 VDC supply, as well as supporting analog or linear circuits requiring multiple power supplies. That means the positive 5V is connected to Vcc and the negative terminal is tied to ground for digital logic. The reference to +/- 15 volts may actually mean two 15 volt power sources required for many linear applications using operational amplifiers, comparators and such. In essence, these circuits require two power supplies +15 volts, - 15 volts and that the two supplies are connected to a ground reference. This means you really have 30 volts rail-to-rail, with a common connection to ground. Attached is a commercial breadboard that shows the wiring terminals as being +5V, +12V, -12V and ground. This is probably similar to what you are referring to and requires 3 different power supplies. Your experiment may only require one voltage power source.

If battery power is the only power source allowed, you really have to determine what kind of voltage/current you need for your experiment. If you are using 5 volt digital logic, you really need 5V +/- 10% supply. Alkaline cells will provide about 1.5 volts/cell, so using 4 cells would create a 6 volt supply. Your IC's may tolerate that, but you might want to reduce the voltage to a lower voltage using 3 cells to produce 4.5 VDC. You may only need 3-6 volts for your experiment if you are using discrete components, in which case, use the 5V terminals of the breadboard. The proto board example suggests that the 5V bus is capable of carrying 1.0 amps of current, where the higher voltage connections are limited to 250 mA.

As to placement of the battery pack, it is really not critical. As you said, observe polarity and everything should be fine.

Rick Marz
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SciKidsMom
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Joined: Sat Feb 27, 2010 4:15 pm
Occupation: Full Time Mom to future engineer w some special needs

Re: BREADBOARD w battery pack sub for regulated power supply

Postby SciKidsMom » Tue Mar 02, 2010 7:55 am

(My son is occasionally supervised by his dad who knows some about electronics but he is working 2 jobs. This is what I was asked to find out:

Using 2 15V sources (9V + 6Vpack) How do I connect to each other & to OP-AP?

Tried tieing positive & negative from the 2 sources together & attach to common ground; the other positive to positive rail & jump to pin 7; the other negative to op-amp pin 4.

Craig_Bridge
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Re: BREADBOARD w battery pack sub for regulated power supply

Postby Craig_Bridge » Wed Mar 03, 2010 12:58 pm

I don't see where you mention which Op Amp part you are using.

Typical Op Amps are either designed to work on a single voltage supply or on a dual voltage supply.

Op Amps that are designed to work on a dual voltage typically have pin outs that are marked something like Vcc/V+ and Vss/V- (not to be confused with the + and - input signal pins). Dual voltage parts usually don't care if you are using +/-6, +/- 9, or +/-15 volts. What the Op Amp is used to drive may care.

A dual voltage supply made out of two nine volt batteries:
Connect the V+ circuit board lead to the plus terminal of one battery (call it the positive voltage source).
Connect the V- circuit board lead to the minus terminal of the other battery (call it the negative voltage source).
Connect the other battery terminals (negative terminal on positive voltage source battery and positive terminal on the negative voltage source battery) together and to any "ground" or "common" circuit point.

A dual voltage supply made out of two six volt batteries would be done the same way just using a pair of 6 volt batteries.

If you require +/- 15 volts, then each voltage source (positive and negative) is made by connecting one positive and one negative terminal together of a six and 9 volt battery. This two battery circuit is then a 15 volt battery "pack" with an unconnected positive and negative terminal. Use two of these 15 volt battery packs as I've described for the 9 and 6 volt versions.

Hope this helps. If you need more help, please provide some additional information on the circuit (hopefully a reference to where we can look at it) and the Op Amp part number.
-Craig


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