DC/DC Converter (Miniature Remote Control Solar Car)

[Nigel Goodwin]

Would like to ask about the inputs of certain circuits, it seems like most of the time, the requirements stated for a specific input of a circuit that can be easily found on books as well as websites are only the voltage input.

Does this mean that one do not need to take the current supplied into consideration?

Sorry if this is another nonsense

It doesn't make any sense because it's too general, you need to ask specific questions.

Your question as it stands is like expecting a couple of paragraphs to give you a three year electronics course!.

But for a precise answer "yes, no, sometimes, may be" :lol:

As your knowledge seems so limited, I'm puzzled as to why you have embarked on such a complicated project? - I'd presumed you were nearing the end of an Electronics course, and this was your teams final project?.

 

[devonsc]

Err...

Ok, ok, sorry. At this moment, I'll first find out about the charging current.

I'll try not to ask anymore stupid question :cry:

Thanks a lot...

 

[williB]

Would like to ask about the inputs of certain circuits, it seems like most of the time, the requirements stated for a specific input of a circuit that can be easily found on books as well as websites are only the voltage input.

Does this mean that one do not need to take the current supplied into consideration?

Sorry if this is another nonsense

have you got a particular circuit in mind?

 

[devonsc]

Hi! The result of the charging current :

Battery used : 12V (as this is what I have at this moment)
Voltage (open circuit) : 19.50V
Charging current approximately : 4.55mA

Does this mean that I'm going to take hundreds of hours to charge a 3400mAH battery?

Does this mean that the solar panel that I've bought is not suitable for my project? :cry:

About the charging circuit, I found this circuit in => **broken link removed**

But it seems like this circuit is no longer posted there when I checked today. Anyway, the following is the attached file:

Any comments about the charging current as well as the charging circuit? I hope genius like you guys could help me out in analyzing the circuit. Err, sorry if I'm not suppose to ask in this manner

Thanks...

 

[williB]

Hi! The result of the charging current :

Battery used : 12V (as this is what I have at this moment)
Voltage (open circuit) : 19.50V
Charging current approximately : 4.55mA

Does this mean that I'm going to take hundreds of hours to charge a 3400mAH battery?

Does this mean that the solar panel that I've bought is not suitable for my project? :cry:

About the charging circuit, I found this circuit in => **broken link removed**

But it seems like this circuit is no longer posted there when I checked today. Anyway, the following is the attached file:

Any comments about the charging current as well as the charging circuit? I hope genius like you guys could help me out in analyzing the circuit. Err, sorry if I'm not suppose to ask in this manner

Thanks...

you have another way to charge the battery, right ?
you could tell your teammates that the best way to charge the battery is to just put a reverse current diode in there... and start working on the battery monitoring circuit...which will be much more fun..and educational in the long run .In My Opinion.

 

[Nigel Goodwin]

Battery used : 12V (as this is what I have at this moment)
Voltage (open circuit) : 19.50V
Charging current approximately : 4.55mA

How bright was the sun?, and was the panel perfectly aligned with it?.

Does this mean that I'm going to take hundreds of hours to charge a 3400mAH battery?

Yes!.

Does this mean that the solar panel that I've bought is not suitable for my project? :cry:

This is what I've been suggesting all along, solar panels have to be huge for any decent output!.

You don't need any kind of charging circuit, as the panel won't supply enough power to overcharge the battery - and the circuit you posted wasn't intended for use with a solar panel anyway.

 

[devonsc]

How bright was the sun?, and was the panel perfectly aligned with it?.

The highest value I obtained in my area is approx. 23V with the charging current approx. 5.63mA.

1.) At this point, I will try to work on a circuit that will enable me to convert an AC Power Supply source to a DC level for the charging circuit. Any advice regarding this? I'm doing this to make sure that there is an alternative way of charging the battery, where I can present it during my presentation.

2.) I'll carry on my work with the solar panel I have in-hand but this time I'll present it in such a way where the solar panel used is just to provide a view or idea on how the entire system of my project works though its not practical to use that particular solar panel that I'm having now for actual application. Any comments?

3.) Err...I still need help in studying the charging circuit posted earlier. Would like to ask regarding the implementation of the 301 IC in the circuit. sorry but do... ...you mind..... ....giving me a hint..... about it? Is the 301 IC there for a simple compensation? so sorry.... (I guess someone is definitely going to "slap" me for asking this)

4.) With reference to the datasheet, I'll try to make use of the 301 IC for the AC/DC converter as well. Any advice?

Thanks a lot to everyone...

 

[Nigel Goodwin]

How bright was the sun?, and was the panel perfectly aligned with it?.

The highest value I obtained in my area is approx. 23V with the charging current approx. 5.63mA.

1.) At this point, I will try to work on a circuit that will enable me to convert an AC Power Supply source to a DC level for the charging circuit. Any advice regarding this? I'm doing this to make sure that there is an alternative way of charging the battery, where I can present it during my presentation.

AC to DC is just a rectifier, assuming your AC is a suitable voltage, other wise you use a transformer before the recifier.

2.) I'll carry on my work with the solar panel I have in-hand but this time I'll present it in such a way where the solar panel used is just to provide a view or idea on how the entire system of my project works though its not practical to use that particular solar panel that I'm having now for actual application. Any comments?

3.) Err...I still need help in studying the charging circuit posted earlier. Would like to ask regarding the implementation of the 301 IC in the circuit. sorry but do... ...you mind..... ....giving me a hint..... about it? Is the 301 IC there for a simple compensation? so sorry.... (I guess someone is definitely going to "slap" me for asking this)

The 301 is a 'comparator', among other things it's monitoring the current to the battery - by measuring the voltage drop across the 0.1 ohm.

 

[williB]

Have you considered using the LM317T ..?
it is an adjustable voltage regulator ..
https://www.electro-tech-online.com/custompdfs/2004/11/LM117.pdf
there are many many examples on how to use it in the data sheet..
MUCH less complicated than your circuit..

 

[devonsc]

Have you considered using the LM317T ..?
it is an adjustable voltage regulator ..
https://www.electro-tech-online.com/custompdfs/2004/11/LM117-1.pdf
there are many many examples on how to use it in the data sheet..
MUCH less complicated than your circuit..

Thanks a lot!

My progress: At this moment, I'll come out with a circuit to convert an AC source of 240V AC to a DC level for the application of the charging circutry posted earlier on. I guess I'll be using nothing more than a full-wave rectifier as well as a centre-tapped transformer. Maybe with a capacitor as well. Any advice? I'll post the circuit as soon as possible to get advice from you guys. Thanks!

 

[devonsc]

Hi there!

I found this circuit but not quite understand the portion circled.
Sorry for my nonsense again.

If my output voltage is sufficient (20V) can i ignore the transformer?

 

[Nigel Goodwin]

Hi there!

I found this circuit but not quite understand the portion circled.
Sorry for my nonsense again.

If my output voltage is sufficient (20V) can i ignore the transformer?

If your output voltage is sufficient you can ignore the whole circuit!, there's no point to it without the transformer. It's a very simple method of increasing the voltage from a solar panel, and it only provides current pulses to the battery, rather than a continuous current.

As you have hardly any power to start with, there doesn't seem much point wasting some of it in the extra electronics.

 

[devonsc]

Would like to list out what am I doing again...hope you dont mind. As shown in the following block diagram.

I was thinking to come out with the proper application of the solar panel as well even though I couldnt implement the solar panel I have now to run this circuit. As I was thinking that I might be able to present the whole idea on how the entire battery charging system works using an appropriate solar panel.

Block diagram 2:
Two different charging circuits to charge the battery.
For the Battery Charging Circuit 2, issit suitable for me to apply the "untitled - Lead Acid Battery Charger"?

 

[Oznog]

OK, here's stuff to know:
1. Sealed lead acid batteries do not like overcharge. Your solar panel's current is so low you will not be able to generate substantial overcharging currents, but your mains charger WILL. Overcharging in sealed lead acids can be prevented by limiting the charging voltage. However, it's not likely to fry your battery before you're done with the project.

2. As you may have noticed from your study of the solar cells, when you graph the voltage vs current, loading it heavier won't get you more current, it just makes the voltage go lower, and the power (voltage times current) is reduced. Basically you can just look at it as a mostly constant voltage device. Changes in sunlight level will change the current you can pull from it without making the voltage drop, but the optimum voltage remains mostly fixed.

3. As noted, you do not have enough current to effectively run a dc/dc converter, the converter takes a few mA to run the 555. Plus there are significant losses in the diode and magnetic core. Plus... well, your converter appears to be a type that doesn't work. Not that I've tried it myself, and I don't totally understand the problem they describe, but these guys detail why the circuit will fail:
**broken link removed**

So the project will be better off with just hooking up the solar cell through a blocking diode straight to the battery. Bottom line.

 

[devonsc]

At this moment, I'm going to take sometime to read up a few matters regarding implementing swithing regulators circuitry to perform the charging and at the same time, improve the efficiency of a that specific circuitry. Any advice? Any suggestions?

Will not be active posting any diagrams at this moment but will still keep track on this post. Thanks a lot.

 

[Nigel Goodwin]

At this moment, I'm going to take sometime to read up a few matters regarding implementing swithing regulators circuitry to perform the charging and at the same time, improve the efficiency of a that specific circuitry. Any advice? Any suggestions?

For a start I would evaluate what you are trying to achieve, charging your battery from the mains you don't really have any efficiency problems, so a switching regulator doesn't really matter - the far greater complexity (and subsequent lower reliability) will out weigh any potential savings.

What is important though, is to avoid over charging the battery, and the mains charger you use should drop to 'trickle charge' once the batter is fully charged - there are many designs available on the net which do this.

As for solar panels, unless you are going to add massive ones, you're not likely to have enough power to over charge a lead acid battery - and you can't afford to waste any power you do have, because as you've found out it's little enough to start with. Even switchmode circuits waste power as well, far better if it all goes in the battery!.

If you do use huge solar panels, which could over charge a battery, you need to provide protection accordingly - usually just dumping the panel power into a large low value resistor is the battery is fully charged. Most of the solar panel charger circuits available do this!.

 

[williB]

thats three people ( including myself)who agree Charging circuit 1 is a diode.. as for charging circuit 2 i suppose that you want to use individual components and do it the hard way..my advice is keep it simple..
And start working on the battery monitor circuit.!!
actually you should design and test the battery monitoring circuit FIRST !!
because once you have that done you can decide how you are going to turn off the charger, when your battery is done...

 

[devonsc]

Hi! I understand what u mean and will work acording to u guys' advice.

I'll put more effort in the monitoring portion.

By the way, would like to ask if theres any suggestion on how do i develop a AC/DC converter by implementing switching regulator?

Any suggestions? Any sample circuits? Please?

Thanks in advance...

 

[devonsc]

Hi again, sorry.

Can I ask this? How to build a AC/DC switching adapter? I know we can easily get one in the market but any advice in building one?

Thanks....

By the way, is there a website or any recommended books that will allow us to refer the types of IC that can be used if we are aware of what forms of circuitry to develop? sorry if this is nonsense...

Thanks....

 

[Nigel Goodwin]

Can I ask this? How to build a AC/DC switching adapter? I know we can easily get one in the market but any advice in building one?

Again, you're not very clear what you are wanting!.

I'm presuming you mean a mains voltage AC to low voltage DC power supply? - in which case the best idea is to consult IC manufacturers datasheets on such devices. However, the biggest problem is likely to be the transformer required, you will probably either have to wind it yourself, or have it custom made - neither method is likely to be cheap or easy!.

To be honest, if you're having to ask about how to do it, you probably shouldn't be attempting it - switch mode power supplies contain high voltages and high frequencies, they can be quite dangerous. Also they are very prone to 'blowing up' - I would expect you to probably get through between five and twenty 'blown up' ones before you get one that works correctly!.

Again, presuming you are only looking for a low power supply, switch mode wallwart type supplies are available for next to nothing - so much easier to use one of those.