hi all,
when i start my car the starter needs a lot of current to operate.So for 3-4 seconds,until the car starts normally,the voltage drops down to 0V and rises up to 12V very quickly because of inductive phenomenon.
I want to construct a voltage regulator 12v or 12,8v maximum input, to 12v output with 2A circuit current maximum.The circuit in normal operation demands 100mA.So ideal steady output is 12v/100mA!
This circuit will provide a small GPS modem..
if someone has a schematic circuit would help me a lot!!
thanks in advance..
when i start my car the starter needs a lot of current to operate.So for 3-4 seconds,until the car starts normally,the voltage drops down to 0V and rises up to 12V very quickly because of inductive phenomenon.
I want to construct a voltage regulator 12v or 12,8v maximum input, to 12v output with 2A circuit current maximum.The circuit in normal operation demands 100mA.So ideal steady output is 12v/100mA!
This circuit will provide a small GPS modem..
if someone has a schematic circuit would help me a lot!!
thanks in advance..
You can't regulate 12 volts to 12 volts with a linear regulator. You would need some kind of a buck-boost capable switching converter to do this. Why would you need 2A output if the load is only 100 mA? That's a big difference.
I would go for a current mode Flyback converter built around an UC3843 control IC. The control circuit can be powered from the output of the own converter, allowing operation down to input voltages as low as 3V once the circuit is started.
If you can read and understand this:Eva said:
http://focus.ti.com/lit/an/slua143/slua143.pdf
then this solution is right for you!
Paulb,
2Á is maximum current.I could use a 2A output fuse in order to protect my modem but in normal condition the circuit operates in 100mA.
So a solid output at 12v/100mA would be best!
2Á is maximum current.I could use a 2A output fuse in order to protect my modem but in normal condition the circuit operates in 100mA.
So a solid output at 12v/100mA would be best!
where does it drop to zero volts?
where are you measuring?
the battery voltage cannot drop to zero or you would not have any current.
where would you get the power to run a smps to run something?
where are you measuring?
the battery voltage cannot drop to zero or you would not have any current.
where would you get the power to run a smps to run something?
So,the voltage drops while cranking the engine,and the GPS restarts?
Hum,I've usually done it with a diode and a large capacitor or small battery.The diode will isolate the cap/battery so that it doesn't discharge back into the car's starter during cranking.
It will 'takeover' and power the device during the voltage dip.
Sort of a simple UPS.
I once used a 17AH SLA in the same setup for a (temporary)car-PC,so it (or more correctly the inverter) wouldn't reset during starting,etc.
Hum,I've usually done it with a diode and a large capacitor or small battery.The diode will isolate the cap/battery so that it doesn't discharge back into the car's starter during cranking.
It will 'takeover' and power the device during the voltage dip.
Sort of a simple UPS.
I once used a 17AH SLA in the same setup for a (temporary)car-PC,so it (or more correctly the inverter) wouldn't reset during starting,etc.
If that's the problem that is to be solved, then this solution (the diode/cap) should be all you need.DigitalJunkie said:
SLA means sealed lead-acid battery. That would work too, but means you need to go buy one to try it.
Maybe the battery is past it's best if the voltage is dropping so low as to reset the GPS. Are you sure you haven't just wired the GPS off the same feed that powers the stereo, which is cut as you turn the ignition key to the cranking position?
That could be an issue also.
But most cars I think dip into the 8-10V range while cranking,atleast IME.
But most cars I think dip into the 8-10V range while cranking,atleast IME.
I think you should also check the state of the cables from the battery to the start engine, this used to be a problem in my car. After I changed them for a lot thicker ones the start engine went real quick on the job...
I don't use the same wires as the stereo to provide my modem.I just take it from a fuse 🙄 ....
I also thought before posting that a detector (diode/capacitor) would be the best combination but i didn't know the accurate diode and and cap i must use.
I will use also the step-up regulator of ''moamps'' after the diode-cap network..
Ha Ha,I think that i solve my problem!!
THANK you ALL!!!!!
I also thought before posting that a detector (diode/capacitor) would be the best combination but i didn't know the accurate diode and and cap i must use.
I will use also the step-up regulator of ''moamps'' after the diode-cap network..
Ha Ha,I think that i solve my problem!!
THANK you ALL!!!!!
I'd suggest putting a choke right at the input, prior to the diode/capacitor. Transient voltages produced by the starter solenoid etc can spike the car voltages a fair deal, causing grief to sensitive electronics...
Cheers
Cheers
Intresting suggestion clem_o!!
But tell me please the value of the choke..
This will affect the diode-cap network?
Can you give me all the values of the parts and the circuit linking?
🙄
best regards..
But tell me please the value of the choke..
This will affect the diode-cap network?
Can you give me all the values of the parts and the circuit linking?
🙄
best regards..
Hi -
Just put the choke before the circuit posted by moamps.
The exact value is not important - you can pull one out of an old car radio, or use the secondary winding of a step-down transformer, i.e. one rated at 2A of current.
Cheers!
Just put the choke before the circuit posted by moamps.
The exact value is not important - you can pull one out of an old car radio, or use the secondary winding of a step-down transformer, i.e. one rated at 2A of current.
Cheers!
12 V supply from car
Sarbein:
I have been using appliance inside a moving vehicle, when start up the engine, It draws over hundred of ampere current, not because the wiring not thick enough, it's because the internal resistance of the lead acid battery. the simple way is just add a diode 5404, filtered with a 2000uf 25V elect. capacitor. this can solve the problem. 2000uf for 1 ampere load.
WE WANT SIMPLE CIRCUIT WITH THE BEST RESULTS
Sarbein:
I have been using appliance inside a moving vehicle, when start up the engine, It draws over hundred of ampere current, not because the wiring not thick enough, it's because the internal resistance of the lead acid battery. the simple way is just add a diode 5404, filtered with a 2000uf 25V elect. capacitor. this can solve the problem. 2000uf for 1 ampere load.
WE WANT SIMPLE CIRCUIT WITH THE BEST RESULTS
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