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tranzol190
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Grumble
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 Posted: Tue Apr 18, 2023 11:52 am Post subject:
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That particular type of diode is a zener diode, and the 5v5 means that if you connect this diode the way it is depicted in this schematic, there will be 5v5 over this diode.
https://en.wikipedia.org/wiki/Zener_diode
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tranzol190
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| Posted: Tue Apr 18, 2023 12:47 pm Post subject:
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| so i need particular model of zener diode which reverese voltage is 5.6v? |
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blue hell
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| Posted: Tue Apr 18, 2023 2:42 pm Post subject:
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| tranzol190 wrote: | | so i need particular model of zener diode which reverese voltage is 5.6v? |
Yes, they have a limit for the power they can dissipate too .. so there seems to be a need to calculate.
With 1kOhm in front and 9V driving it .. 9V - 5V6 -means> 3.4V over 1kOhm -andthatmeans> 3.4mA through both the zener and the resistor ... roughly .. and so over 5v6 -> 19 mW (using power = current times voltage) .. so eh .. any 5v6 zener will do .. lowest rating would be 50mW or so I think.
May that be clear enough & yet not too wild :)
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also .. could someone please turn down the thermostat a bit.
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tranzol190
Joined: Apr 18, 2023
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| Posted: Sun Apr 23, 2023 9:45 am Post subject:
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| Thanks for your explanation. Could explain me what this diode is doing in the circuit |
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PHOBoS
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| Posted: Sun Apr 23, 2023 2:58 pm Post subject:
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The diode is part of a fairly standard regulated supply circuit. You don't see it used that much anymore since
single package linear voltage regulators are more stable and convenient. These days those are also being used
less because switching regulators are more efficient.
The zener diode in combination with the 1K resistor provides a stable voltage of 5.6V. The potentiometer and resistor
that are connected to it create another voltage divider. Assuming both are 47K that means it can be adjusted between
5.6V and 2.8V. This voltage is then buffered by the transistor which is configured as an emitter follower aka voltage follower.
There is a bit of a voltage drop over the transistor so the output can be roughly varied between +2.5V and +5V.
more info on regulated supplies using a transistor and zenerdiode: https://www.bristolwatch.com/ele/zener_power_supply.htm
(or do a search for "regulated supply zener diode transistor")
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tranzol190
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| Posted: Mon Apr 24, 2023 4:10 am Post subject:
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I've bulid allready your Nandulator and wanted to apply starve part of this cicuit to it.
In description of the circuit ( in the link) is written that there is 5v to 1v regulation, se maybe there is different pot. I don't have any zenner here, but few L7805 5v regulators, can i some how use it to get similiar effect? |
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tranzol190
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| Posted: Tue Apr 25, 2023 2:21 am Post subject:
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| Can i just put L7805 insted zenner diode and 1k resistor, and then transistor on the output of L7805? |
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blue hell
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| Posted: Tue Apr 25, 2023 4:06 am Post subject:
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| tranzol190 wrote: | | Can i just put L7805 insted zenner diode and 1k resistor, and then transistor on the output of L7805? |
Yes, can do .. otoh a zener costs near to nothing.
And you'd want to keep in the resistor and the pot before the transistor .. as that makes it regulated voltage.
Also, you might want to add a (normal) diode between the regulator's ground pin and ground to get the same voltage range. The diode needs to conduct then, so .. arrow pointing to circuit ground. It then will lift up the 7805 output to 5v6 / 5v7 or so.
Then the 5v6 / 1k has one other function .. it allows enough current to flow in the power line for the LED to light up (and that one also protects against reversed battery connection). This is not functional though for the basic operation, it is just to see that he circuit is on, but might you want it .. you may want to add a resistor after the LED to ground .. something like 2k2 maybe .. or larger/smaller when there is too much/not enough light.
Might you not want a light, a normal diode there would do.
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also .. could someone please turn down the thermostat a bit.
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tranzol190
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tranzol190
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| Posted: Tue Apr 25, 2023 6:31 am Post subject:
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| I build what is on the drawing and find out that regulator causing significant voltage drop battery is weak like 5v. So think i will look for zenner. Thank you for your help |
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blue hell
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| Posted: Tue Apr 25, 2023 6:49 am Post subject:
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| tranzol190 wrote: | | Like this? |
Heh, no .. there should not be a 2k2 at that place ... regulation will not work then - the diode is OK though.
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Jan
also .. could someone please turn down the thermostat a bit.
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