No. And the resistor will burn up.
You need > 2VDC across the 78L05 to regulate, so use 3V drop across it, then the 78L05 dissipates 3V x 0.1A = 0.3W.
Then there is 24V - 5V - 3V = 16V to drop in the resistor.
So 16V / 0.1A = 160 Ohms. There's 16V x 0.1A = 1.6W actual dissipation in the 160 ohm resistor, so use a 3W part.
Use a series 160 ohm 3W resistor. Also use a decoupling capacitor 0.33uF near the regulator.input terminal.
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If the heat from the 3W resistor is a nuisance, you could always use one of these as pre-regulator :
https://www.aliexpress.us/item/3256802944105330.html
I think the max input voltage is 24V though so a couple of IN4001 in series with its input I'd use to stay safe. You'll need the 'adjustable' setting and twiddle the preset pot to give 8V out.
https://www.aliexpress.us/item/3256802944105330.html
I think the max input voltage is 24V though so a couple of IN4001 in series with its input I'd use to stay safe. You'll need the 'adjustable' setting and twiddle the preset pot to give 8V out.
If you need small, how about these step-down converters designed as drop-in replacement for 78xx:
https://www.pololu.com/product/2843
https://www.pololu.com/product/2843
a series resistor to the7805, transfer the heating from the regulator device to the resistor..
just make sure that there is enough input output voltage on the regulator device for it wo work fine....
just make sure that there is enough input output voltage on the regulator device for it wo work fine....
Similar to above is the Sanken br300. 5v/1A I've used them for several projects. I think there is quite a selection of dropin 78xx switchers out now.
That looks cute, I wonder what the tiny buck reg chip they're using is?
Here's the one I linked next to an LM317, not that much larger :
They're much bigger than a TO92 for sure but that's mainly because they're much higher rated, current-wise. I had a look but none I've seen is rated at 0.1A - if one were available it would be a lot smaller than these.
I have been looking (on Taobao and Aliexpress) and haven't seen one yet. I guess there isn't a market for TO92 replacement regulators because no heatsink is normally used with them so no need for switchers to replace them. The smallest I'm seeing are TO220 replacements.
5V x 0.1A = 0.5W, so the resistor should be able to take at least that much current.
I would use a plain 7805, those are good to 1A, I think, and a 3W resistor.
I have seen BT131 in TO-92, but those are triacs.
Space permitting, or not, use on old cell phone charger, from the Nokia 3315 days, those are good to only about 0.5A, and quite stable. You could discard the housing, and fit the circuit inside your device.
The 24V is for the power amp section of your device?
Unless it is Class D, there should be enough space inside to fit a regular 7805...and ventilation / air flow are always important.
I would use a plain 7805, those are good to 1A, I think, and a 3W resistor.
I have seen BT131 in TO-92, but those are triacs.
Space permitting, or not, use on old cell phone charger, from the Nokia 3315 days, those are good to only about 0.5A, and quite stable. You could discard the housing, and fit the circuit inside your device.
The 24V is for the power amp section of your device?
Unless it is Class D, there should be enough space inside to fit a regular 7805...and ventilation / air flow are always important.
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True, it is also cheaper with a 78XX equivalent and a resistor and maybe a cap.
A TO220 sized miniboard "gigantic"???
Sorry but not the first time your requirements (power/dissipation/size) turn out to be quite unrealistic.
That being polite.
Absolutely fine. I think the M versions were 0.5A and were commonly seen in lots of home entertainment gear like VCR's. They are a T0220 package so perfect.
Also using a series Zener such as a 8v2 1.3 watt type will reduce the voltage the reg sees by 8.2v (so 19-8.2 = 10.8 volts) and that will make the reg run much cooler (even your 78L05). The Zener still gets warm but splits the heat dissipation between the reg and the diode.
Dissipation in the reg falls from 1.4 watts @ 100ma with a 19v supply to just 0.58 watt with the Zener. The Zener gives a more constant input voltage to the reg if the load current varies.
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