“I wish to assemble a bargraph display to indicate approximately 25volts dc.How many LM3914 I should cascade? How to calculate resistor value which is grounded from the junction of Pin 6 & 7 (Rhi &Ref.out)? Assuming i need to cascade 3 LM3914s,what is the method to cascade these ics? The display need not be precise or very bright. I hope you can help me out.”
“I shall be very grateful. Can we do it in such a way that the first LM3914 displays 1-10 v & second 11-20v & the third 21-30v?”
Thank you again – Mail from AD
Reply from delabs
Have a look at the TI application note which has many examples. Understanding this will help you make your own solution.
20-Segment Meter with Mode Switch
Cascading is required if you want more resolution. Example for measuring 20V, you want to show in 1V per LED steps. It can withstand +/- 35 Volts input upper limit.
The inbuilt reference is 1.2V use it as shown in the Typical Application. This also helps in setting the brightness of LED display. You may need to use external attenuators, buffers or precision rectifiers to measure AC voltages or High Level DC voltages.