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who know why LM334 apply in this circuit?

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Hero999

Banned
Why do you want to add an LM334?

What are you intending to achieve?

The circuit on page 12 of the datasheet is a temperature controller whciih reliase on the fact that the LM334 is temperature sensitive.

The circuit you attached has nothing to do with the LM334.
 

mneary

New Member
The LM334 provides about 2.3 mA (as shown in the schematic) to the LM350's Vreg pin. Flooded lead acid batteries prefer lower charging voltages at higher temperatures to reduce gassing.

The temperature sensitivity of the LM334 (in this circuit, about 7 uA/ degK) is apparently used to compensate for this. One would hope that the LM334 isn't heated by the charger circuits and is otherwise in a similar ambient as the battery.

The website owner specifies a calibration temperature of 25 degC, which must be obeyed to make this work properly.
 

hcchuar

New Member
The LM334 provides about 2.3 mA (as shown in the schematic) to the LM350's Vreg pin. Flooded lead acid batteries prefer lower charging voltages at higher temperatures to reduce gassing.

The temperature sensitivity of the LM334 (in this circuit, about 7 uA/ degK) is apparently used to compensate for this. One would hope that the LM334 isn't heated by the charger circuits and is otherwise in a similar ambient as the battery.

The website owner specifies a calibration temperature of 25 degC, which must be obeyed to make this work properly.
I have a bit blur about this,
"lower charging voltages at higher temperatures to reduce gassing."

LM334 is set 2.3mA for this circuit,25C, how can get a higher temperature?
 
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Hero999

Banned
Sorry I didn't look at the schematic as well as I should have when I made my previous post.

Yes, the LM334 is responsible for adjusting the voltage to compensate for the temperature change in the voltage across the battery.
 

hcchuar

New Member
Sorry I didn't look at the schematic as well as I should have when I made my previous post.

Yes, the LM334 is responsible for adjusting the voltage to compensate for the temperature change in the voltage across the battery.
When the battery is charging, temperature inside battery will increase as well, so need use LM334 to compensate?this is what u means?

if the battery temperature is increase until 30C as a example, the circuit 2.3mA still assume battery temperature is 25C? or the current will increased as well?
 

Hero999

Banned
It isn't the current that's increased it's the voltage. Ideally lead acids should be charged to a higher voltage at higher temperatures.
 

mneary

New Member
When the battery is charging, temperature inside battery will increase as well, so need use LM334 to compensate?this is what u means?

if the battery temperature is increase until 30C as a example, the circuit 2.3mA still assume battery temperature is 25C? or the current will increased as well?
The LM334 senses the surrounding air (ambient) so that on a very hot day the charging voltage is reduced, and on a very cold night the charging voltage is increased. The LM334 is not arranged to sense the short term changes in battery temperature.

This is useful if the charger is used outdoors (charging a car battery in situ) in climates where the temperatures may range from -30C to +30C such as where I attended school near Massena NY.
 

Boncuk

New Member
I think it is just a precise current source to achieve a precise reference voltage for two different kinds of batteries via the burden resistors.

Boncuk
 

mneary

New Member
The LM334 is not a precise current source. I studied this in depth for my own knowledge but didn't publish details so as not to confuse the OP. In this circuit, the tempco is about 7 uA per degree K. The result is a temperature coefficient at the voltage regulator which matches the changing needs of a flooded lead-acid battery across climate differences. I don't think this is just lucky.

A resistor alone (P1, R4, and P2, R5) would achieve a precise voltage reference for each battery voltage.
 
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