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.

Need to vary PSU from 24V to 27V

Status
Not open for further replies.

cupoftea

Advanced Member level 5
Joined
Jun 13, 2021
Messages
2,507
Helped
53
Reputation
106
Reaction score
108
Trophy points
63
Activity points
13,088

1642418653520.png


Vo = mRpot + Voff, Rpot in ohms, m in Volts/Ohm, so at 0 ohms (assuming you have the 27V supply)

so Voff at 0 ohms = .7 x 27 volts = 18.9V

@ 1.8K ohms

(.9)(27) = m1800 + Voff = 1800m + 18.9 = 24.3

So m = (24.3 – 18.9) / 1800 = .003

So we have Vout = .003 x Rpot + 18.9 or Rpot = (Vout – 18.9) /.003

So at 24V Rpot = (24 – 18.9) / .003 = 1700 ohms
So at 27V Rpot = (27 – 18.9) / .003 = 2700 ohms

So pot wants to range from 1700 ohms to 2700 ohms,.

So use a series R of 1700 ohms with 1000 ohms pot.

This is approximate because their graph shows linear behavior, except 100% out of supply is
infinite R which is not linear with the graph.


Regards, Dana.
 
Datasheet doesnt offer much guidance from 90% to 100%...might there be a big tolerance also in this region?
Rather systematic nonlinearity than tolerance. But you can't estimate the behaviour without assuming a circuit model. An obvious model would be a pot with an internal series resistor put in the voltage divider. Enough points to fit divider ratio, divider impedance and series resistor. Or assume a divider for the reference voltage.
 
Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top