Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Threshold settings using Pushwheel Switches

Status
Not open for further replies.

gary36

Full Member level 4
Joined
Mar 31, 2018
Messages
208
Helped
0
Reputation
0
Reaction score
0
Trophy points
16
Activity points
1,806
I have an analog comparator, whose threshold should be variable from 1mV-9999mV. Condition is that , this setting should be nonvolatile in nature. I have been thinking various options including potentiometer , pushwheel switches + DAC . The issue with pushwheel is that , ganged version is not available in common. is there a better way to set threshold?. (I cannot use any controller in this project)
 

Hi,

Is that a trigger threshold? I don't know much about comparators but if so, 1mV seems maybe unrealistic in the real world. Trimpots drift a lot maybe for a nonvolatile setting, perhaps even if the trimpot is used for some kind of one-time calibration and the screwhead glued in place after - I guess the application has no movement or vibration; they also drift a fair bit with temp.

Sorry I can't offer an especially usefully helpful answer.
 

As there's no DAC with BCD input, you need decimal to binary encoding logic at least. If implemented by processor, PLD or huge discrete IC circuit is a matter of taste. Potentiometer with 4 decades resolution is demanding.
 

What is the best settings possible using a precision rotary pot? can we achieve 10mV ( 0-10V range)? Besides I wass thinking of LUT to convert BCD to binary, but unfortunately parallel EEPROM have become obsolete.
 

Hi,

can we achieve 10mV ( 0-10V range)?
This is 1/1000of full range.
A standard pot has about 300° rotation angle. So can you adjust the pot's wiper precisely down to 0.3°?

Klaus
 

Ok, it is clear. How about LUT method?
 

Hi,

A BCD switch has 4 outputs. With the significance of 1, 2, 4, 8
One could connect
MSB to a 10k resistor
Bit 2 to a 20k resistor
Bit 1 to a 40k resistor
LSB to a 80k resistor and use an Opamp circuit to generate an analog voltage.

Do this for all four BCD nibbles.

Then use another OPAMP to add the 4 analog voltages but with significance of 1, 10, 100, 1000

You need very precise resistors, good OPAMPs and I recommend to use a voltage reference, because the supply voltage isn't stable enough to get good results.
*****

I wonder why you asked about 10mV of 10V, because this is only three decades, but before you speak about four decades.

Klaus
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top