DC/DC Converter (Miniature Remote Control Solar Car)

[williB]

Hi there, I've read about the implementation of transformerless AC/DC converter. Not implementing this in the project, just want to ask something this form of AC/DC converter.

...

the microchip site has a transformerless powersupply design ,but it is anly good for a few mA..that the PICs use..
did u order your PIC ?

 

[devonsc]

the microchip site has a transformerless powersupply design ,but it is anly good for a few mA..that the PICs use..
did u order your PIC ?

Thanks, I will read up more from there.

About the PIC microcontroller, I can only get them this Friday as my class ends late today and late as well for tomorrow. Thursday is a public holiday here. I'll be getting a unit of 16F648A and a unit of 16F628. Thanks...

 

[williB]

the microchip site has a transformerless powersupply design ,but it is anly good for a few mA..that the PICs use..
did u order your PIC ?

Thanks, I will read up more from there.

About the PIC microcontroller, I can only get them this Friday as my class ends late today and late as well for tomorrow. Thursday is a public holiday here. I'll be getting a unit of 16F648A and a unit of 16F628. Thanks...

you are going to need to get a programer , or make one --find a nice parallel programer..

 

[devonsc]

As shown is the circuit I intend to use for my one of my charging circuitry for the battery where the source is from a solar panel.

The input of this circuit, the solar panel, will not be the one seen or tested earlier, which is one with low output current.

Would like to ask the following questions:

a.) How do I determine the appropriate value of the capacitor as well as the inductor? Can I use approximately 10 microFarad for the capacitor? As for the inductor, is approximately 100 miliHenry an appropriate value?

b.) Issit advisable to include a zener diode in parallel with the Load as well as the capacitor?

c.) Should I boost to a voltage level of 15V for charging purposes in this circuit?

d.) With an approximate current value of 40mA, power output of 0.3W, voltage output of 7.5V, can this circuit be operated?

Need advice...Thanks a lot...

Sorry for not including the arrows to denote the flow of current...

 

[williB]

As shown is the circuit I intend to use for my one of my charging circuitry for the battery where the source is from a solar panel.

The input of this circuit, the solar panel, will not be the one seen or tested earlier, which is one with low output current.

Would like to ask the following questions:

a.) How do I determine the appropriate value of the capacitor as well as the inductor? Can I use approximately 10 microFarad for the capacitor? As for the inductor, is approximately 100 miliHenry an appropriate value?

b.) Issit advisable to include a zener diode in parallel with the Load as well as the capacitor?

c.) Should I boost to a voltage level of 15V for charging purposes in this circuit?

d.) With an approximate current value of 40mA, power output of 0.3W, voltage output of 7.5V, can this circuit be operated?

Need advice...Thanks a lot...

what is the "clock pulse" ??
if it a switch .. why not just use a switch..???

 

[devonsc]

Sorry if its not right but I was thinking of the following operation:

Where if I were to use a transistor as a switch to generate ON and OFF instead of having a manual ON or OFF switch.

Coz I thought when the switch is ON, the current will flow across the inductor and causes the current to increase? Then when the switch is OFF, the current will charge up the capacitor to a voltage higher than the input voltage?

Meaning, to have somekind auto charge and discharge of the capacitor thingy. Is this wrong? Mind correcting me? :cry:

 

[devonsc]

If I can apply the attached circuitry, any advice regarding the following matters?

a.) How do I determine the appropriate value of the capacitor as well as the inductor? Can I use approximately 10 microFarad for the capacitor? As for the inductor, is approximately 100 miliHenry an appropriate value?

b.) Issit advisable to include a zener diode in parallel with the Load as well as the capacitor?

c.) Should I boost to a voltage level of 15V for charging purposes in this circuit?

d.) With an approximate current value of 40mA, power output of 0.3W, voltage output of 7.5V, can this circuit be operated?

Thanks...

 

[williB]

Sorry if its not right but I was thinking of the following operation:

Where if I were to use a transistor as a switch to generate ON and OFF instead of having a manual ON or OFF switch.

Coz I thought when the switch is ON, the current will flow across the inductor and causes the current to increase? Then when the switch is OFF, the current will charge up the capacitor to a voltage higher than the input voltage?

Meaning, to have somekind auto charge and discharge of the capacitor thingy. Is this wrong? Mind correcting me? :cry:

Nice try .. but it seems like you are trying to get something from nothing .
i thought we allready decided that the best /simplist method to charge the battery with the solar pannel was a diode..!!!

 

[devonsc]

Hi!

Nice try .. but it seems like you are trying to get something from nothing .
i thought we allready decided that the best /simplist method to charge the battery with the solar pannel was a diode..!!!

Yea, but I thought of getting a new solar panel that has the following characteristic:

Load voltage: 7.5V
Typical current at load voltage: 45mA
Output power: 0.3W

I'm trying to order this solar panel to run a test on it. However, at this stage, I'm allow to assume that this is the panel that I have for my project and develop a circuitry to implement this panel for charging. Since I will be charging a 12V battery, thought I'm suppose to first boost the voltage level to approximately 15V?

Hence, I come out with that circuit.

 

[devonsc]

No longer using the 133mW solar panel

By the way, I am now allowed to do the following:

I can ignore the solar panel I have bought and develop a charging circuit that assumes that I have the appropriate solar panel in hand for my project. As long as I manage to search for the datasheet for the appropriate solar panels.

Meaning, I was thinking to ignore using the previous solar panel that I've bought, the one with 133mW output and search for a better one to reduce the charging time for the 12V battery. (approximately 6400mAH)

 

[Nigel Goodwin]

Re: No longer using the 133mW solar panel

By the way, I am now allowed to do the following:

I can ignore the solar panel I have bought and develop a charging circuit that assumes that I have the appropriate solar panel in hand for my project. As long as I manage to search for the datasheet for the appropriate solar panels.

Meaning, I was thinking to ignore using the previous solar panel that I've bought, the one with 133mW output and search for a better one to reduce the charging time for the 12V battery. (approximately 6400mAH)

That sounds a far better idea, and for the purposes of the project will work just as well - simply simulate the solar panel using a variable power supply!.

I'll be interested to see how large a 6400mAH panel will be!.

 

[devonsc]

That sounds a far better idea, and for the purposes of the project will work just as well - simply simulate the solar panel using a variable power supply!.

I'll be interested to see how large a 6400mAH panel will be!.

Hi, sorry as I don't quite understand what you mean here. About how large a 6400mAH panel will be, I thought it depends on the characteristic of the panel? As attached is two spec list, the first specification list is actually a single crystalline cell which has the ability to provide great output whereas the second specification sheet is a panel that shows the output as circled. (there is an error regarding the short circuit current, i think)

So you mean how large as in the size of the panel?

 

[devonsc]

Sorry, here is the other spec sheet...

Guess there is something wrong with the short circuit current. Is there a mis-print? Isn't it suppose to be higher?

 

[devonsc]

By the way, just asking...not for the project. Just asking if the solar cell is available in the market, the attachment entitled SP. Issit possible to step-up the voltage to a level of 14-15V for battery charging purposes?

Through calculations, I get a value of Duty Ratio of 0.96. Is it possible to have a Duty Ratio of approx. 0.96 for the DC/DC boost converter?

 

[Nigel Goodwin]

Sorry, here is the other spec sheet...

Guess there is something wrong with the short circuit current. Is there a mis-print? Isn't it suppose to be higher?

Looks like it to me!.

And yes, it was the physical size I was asking about, but I see the panel you've circled is only 330mW. I also don't see the relation between that spec sheet and the previous picture?.

 

[devonsc]

And yes, it was the physical size I was asking about, but I see the panel you've circled is only 330mW. I also don't see the relation between that spec sheet and the previous picture?.

Yup, I posted two pieces of spec sheet actually. The first one is, entitled SP is a single crystalling solar cell which provides good outpput whereas the other spec sheet, SP2 (circled) is the regarding the solar panel which has the output of 0.3W. About the SP2 spec sheet, I will reconfirm with the distributor as soon as possible regarding the output short circuit current listed in the SP2. It states that the output short circuit current was 35mA, which is lower than the typical current and load voltage. Is this a mistake?

Regarding the physical size, I thought another aspect to look into would be the duration taken to fully charge the 12V battery?

Can I put it in this way? By just using one solar cell (spec sheet entitled SP, the dimension as stated in the spec sheet), I will be able to charge the 12V battery in approximately 1 and a half hour?

As for the other panel, (SP2 with one panel's output current at load voltage is 45mA) by using a total number of 5 units.
So => 45mA X 5 = 225mA
Thus => 6400mA / 225mA = approx. 29 hours

The size of a unit is => 150mm by 55mm. Thus, the size of a total of five units of this panel would be around => 150mm by 275mm.

Hope this is what you want.

But there are other solar panels that will provide a better output compare to the one circled in SP2. Just like the column, SA-03300, on the left of the SA-0640. In which this unit is approximately => 150mm by 110mm.

 

[devonsc]

By the way, just asking...not for the project. Just asking if the solar cell is available in the market, the attachment entitled SP. Issit possible to step-up the voltage to a level of 14-15V for battery charging purposes?

Through calculations, I get a value of Duty Ratio of 0.96. Is it possible to have a Duty Ratio of approx. 0.96 for the DC/DC boost converter?

Just asking...is this practical? I will try out as well. Thanks.

 

[williB]

By the way, just asking...not for the project. Just asking if the solar cell is available in the market, the attachment entitled SP. Issit possible to step-up the voltage to a level of 14-15V for battery charging purposes?

Through calculations, I get a value of Duty Ratio of 0.96. Is it possible to have a Duty Ratio of approx. 0.96 for the DC/DC boost converter?

Just asking...is this practical? I will try out as well. Thanks.

how can i say this .?
NO it is not practical to use a DC/DC converter .
Forget you ever heard of a DC/DC converter.
Because you would be using up Your Limited CURRENT to boost the voltage.

 

[devonsc]

General question on solar car

Would like to ask a general question here. Nothing to do with project.

how can i say this .?
NO it is not practical to use a DC/DC converter .
Forget you ever heard of a DC/DC converter.
Because you would be using up Your Limited CURRENT to boost the voltage.

For an actual solar car:
From the solar panel, which will be used for charging a specific 12V battery. Is it true that the actual implementation of Boost DC/DC Converter is to step-up the voltage of the solar panel (assuming the voltage is lower than 12V battery)? Since we need a higher voltage from the charging circuit to charge the battery, a flow of current from high voltage to low? Is this right? Mind to comment?

Thanks a lot

 

[Nigel Goodwin]

Re: General question on solar car

From the solar panel, which will be used for charging a specific 12V battery. Is it true that the actual implementation of Boost DC/DC Converter is to step-up the voltage of the solar panel (assuming the voltage is lower than 12V battery)? Since we need a higher voltage from the charging circuit to charge the battery, a flow of current from high voltage to low? Is this right? Mind to comment?

Yes, that's right - but don't forget, increasing the voltage with a DC/DC converter also decreases the current - so if you have 10V at 1A, and boost it to 20V, you will only have 500mA (actually more like 450mA, due to losses).