Hi,
I am struggling since a week , i am trying to use a darlington array ic ULN2803A in series (taking the voltage from the GND pin 9) since as i understand the Darlington array switches the collector that is feeded with LOW from the MCU to the ground , and i want to use that as a voltage selection circuit
i have multiple choises 24v ,12v 5v and ... as shown below , will it work ?
and about the COM pin usually it is connected to the supply voltage , wich one should i connect with COM now !
Edit : forgot to mention that if A1 is High A2 is LOW and vice versa
What is that circuit? How much current will it draw?
a device that works on one of the signals or voltages (whatever the device is) and the power source is external it may be a 24v battery
the current is limitted to 50ma
and relays will make the circuit bigger i want it to be small and portable
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Perhaps you could use PNP transistors like bc327. You could use the ULN to drive the base pins of the transistors.
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well, what im trying to do is to avoid using transistors NPN or PNP , i could use 64 bc547 transistors
for the external device don't require any push-pull driver
I think you need to define your specification a bit tighter - how many voltages do you want to measure , how accurately and why ?
The “64” transistors is odd ?
Don’t dismiss relays without a bit of research - you can get small dil packages, Uni selector (?)
You will need potential dividers to keep voltages low ( 5v or 1.1v) at the processor input .
NPN transistors feed the base with current and i don't want this , i have a connector with 6 pins each pin may provide 24v or12v or 5v .... I did the count and it needs 64 transistor
I am not asking whether i should NPN or PNP , i am chasing to reduce the number of transistors and it comes to my mind using darlington array ic's in series (getting one of voltages from the GND)
The voltage conditionning is all done
I am focusing on how to reduce the amount of transistors used as switches
64 transistor is the overall count
I want the mcu to give a signal and basing on that signal one of (many) voltages is chossen to be passed to a pin of a connector
The connector contains 6 pins
I could use voltage (24v for example) ->transistor collector->transistor emitter to a pin
And so for each voltage and with commun emitter to each single pin the amount of transistors is gonna be crazy
Relays take space and they're mechanical and i want a soft switching
You haven’t said anything about the project and why you need 64 Transistors , and to what accuracy do you want to measure the voltage.
You will get better advice if you let us know what you are doing and why ( as there might be a better way ).
BTW look at matrices . 64 combinations can be got from 8x8 ( that’s 16 connections )
I need 64 transistor because a have a 6 pin connector and each pin of the connector gonna provide one of multiple voltages or signal, i want to redirect this voltage/signal to it's relevant circuitry based on a signal comming from arduino
Some of these signal is intended to be measured 0-5v or 4-20ma or frequency or even ground (the ground of the pluged device) 24v or 12v to be verified or shorting pins of the connector
I want the project to small
I don't think more details are needed since the idea is to redirect the voltages comming from the connector
