How to tell current drawn from a schematic

In summary, NascentOxygen suggests that a transformer capable of drawing 370 mA should be able to power a VCO. If the VCO is to be amplified, then amplification will need to be external. Power supplies are always handy to have, so if you're going to tackle the more ambitious project of making your own power supply, then a kit like the one mentioned is a good place to start.
  • #1
asteinhorn
3
0
Hi all,
I am relatively new to the EE field, and while looking at the schematic for a VCO, I had the following question; if i wanted to build a bipolar power supply using a transformer for the VCO, what current should said transformer be able to draw? More specifically, how can I tell the maximum current the VCO will draw by looking at the schematic? I got the schematic from birthofasynth.com, and I will post a link to it below:

http://goo.gl/88KuQ

Any comments/help would be greatly appreciated. Not to be picky, but I would prefer an explanation to an answer, that I may be able to learn and use the knowledge in future.

Thanks!
 
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  • #2
Hi asteinhorn! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif

If you do build a regulated power supply, you'll be using a published design so won't it specify the transformer to use?

If I were constructing from scratch, I think I'd just allow, say, 10mA per amplifier (the triangles), then double that to allow oodles of margin.

But if you want to be more precise, have a look at the data sheets for those ICs and see what you are told about their currents. You have a quad amp, a dual, and the PLL chip. The transistors will use power, too, of course, at a guess, 40mA total for them should be plenty.

Sorry if I'm too rough 'n ready for you were hoping. If it's important not to overdesign, your best bet might be to build the circuit then measure its current needs, before looking for a power supply.

It seems an ambitious first project, for someone new to electronics.
 
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  • #3
Hi NascentOxygen,

Thanks for the quick reply! By your suggestions, it would appear I'd need about 370 mA to be safe. Should I take into account any amplification of the output signal, or will that process be entirely external (i.e. feeding it through a dedicated amplifier)? Thanks again.

By the way, I'm aware that this project is perhaps overly ambitious for a novice such as me (this isn't my first foray into EE, but it is my first significant one), but at least I'll learn something if I fail. That's all that counts, right? :)
 
  • #4
asteinhorn said:
By your suggestions, it would appear I'd need about 370 mA to be safe. Should I take into account any amplification of the output signal, or will that process be entirely external (i.e. feeding it through a dedicated amplifier)?
It sounds a lot when you put it that way, I'd be surprised if it drew over 100mA, but I did say to err on the high side. The 4046's are available in various flavours, including some low-power versions which one would choose for a gadget to be powered by battery. The main current users will be the IC amplifiers.

The VCO will draw a bit more current when you connect it to an amplifier, but that amp will have its own power supply with a lot more grunt.

Power supplies are always handy to have, maybe you could instead make your first project the assembly of something like a 0-20v 2 amp bipolar regulated power supply kit, where everything is provided, including the board on which the parts need to be assembled? (No, I don't have any particular kit in mind.) You could then assess whether you are up to tackling the more ambitious project.
 
  • #5
NascentOxygen said:
Power supplies are always handy to have, maybe you could instead make your first project the assembly of something like a 0-20v 2 amp bipolar regulated power supply kit, where everything is provided, including the board on which the parts need to be assembled? (No, I don't have any particular kit in mind.) You could then assess whether you are up to tackling the more ambitious project.

That's not a bad idea at all. I've done some smaller EE projects and I know my way around a schematic (rudimentarily, at least), so I think I'll try to tackle the power supply project, either via kit or with perf-board and an online schematic. Thanks very much for your help and suggestions. I really appreciate it.
 

1. How can I determine the current drawn from a schematic?

The current drawn from a schematic can be determined by analyzing the circuit and calculating the total current flowing through it. This can be done using Ohm's law (I = V/R) or Kirchhoff's current law, depending on the complexity of the circuit. Additionally, you can also measure the current using a multimeter.

2. What factors affect the current drawn from a schematic?

The current drawn from a schematic can be affected by various factors such as the voltage source, the resistance of the components in the circuit, and the type of components used. The current drawn can also be influenced by external factors such as temperature and humidity.

3. How do I interpret the current values on a schematic?

The current values on a schematic represent the flow of electrical charge through the circuit. They are usually denoted in units of amperes (A) and can be either positive or negative depending on the direction of current flow. In general, higher current values indicate a larger flow of charge through the circuit.

4. Can I use a schematic to predict the current drawn in a real circuit?

While a schematic can provide an estimate of the expected current drawn in a circuit, it may not always be accurate. This is because real-world circuits may have variations in components, manufacturing defects, and other external factors that can affect the current. It is always recommended to measure the current in a real circuit to get an accurate reading.

5. How can I reduce the current drawn from a schematic?

To reduce the current drawn from a schematic, you can use components with higher resistance values, use a lower voltage source, or add resistors in series or parallel to the circuit. Additionally, optimizing the design and layout of the circuit can also help in reducing the current drawn. However, it is important to ensure that the desired functionality of the circuit is not compromised while reducing the current drawn.

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