Maths help....Again...exp? - Page 4 - UK Vintage Radio Repair and Restoration Discussion Forum

GrimJosef · 9th Apr 2019, 7:16 pm

My Windows10 calculator looks like the attached pic. What you have to do is to open the menu A and select Scientific from the drop-down. Then click on the arrow B until you get the screen in my pic. Then enter the number you want, say 0.03334, and click the e^x button, C, which will get you exp(0.03334). If you want exp(-0.03334) then you can use the plus/minus key, D, when you enter the number.

Cheers,

GJ

ms660 · 9th Apr 2019, 7:43 pm

Brill, many thanks, had the scientific already but didn't know there were more keys, thought it was just exp not ex as well, anyways just done that exercise for 0.03334 and it returns the correct answer, eureka!

Next, a step by step instruction for the procedure to do the calc using the original formula, can you help with that?

Original formula...Vr=(Vp-0.7)(1-exp(-T/CR)) I can do Vp-0.7 no problem, I can also do T/CR no problem, the answer should be 0.47 volts or thereabout using that formula with the following inputs...Vp=15 volts...T=0.01667 secs...R=5,000 ohms...C=100uF

Lawrence.

Skywave · 9th Apr 2019, 9:01 pm

I use MS Excel for all sorts of formulae that arise in electronics. This attachment might help . . . .

Al.

ms660 · 9th Apr 2019, 11:10 pm

I think I've figured it out now using the Windows 10 scientific calc now that I've found the ex function and I find it faster using the formula derived by GJ from my original alternative method, is that coincidence or is there a faster way using the original formula?

Lawrence.

9th Apr 2019, 7:16 pm	#61
GrimJosef Dekatron Join Date: Sep 2007 Location: Oxfordshire, UK. Posts: 4,311	Re: Maths help....Again...exp? My Windows10 calculator looks like the attached pic. What you have to do is to open the menu A and select Scientific from the drop-down. Then click on the arrow B until you get the screen in my pic. Then enter the number you want, say 0.03334, and click the e^x button, C, which will get you exp(0.03334). If you want exp(-0.03334) then you can use the plus/minus key, D, when you enter the number. Cheers, GJ Attached Thumbnails __________________ http://www.ampregen.com Last edited by GrimJosef; 9th Apr 2019 at 7:24 pm.

9th Apr 2019, 7:43 pm	#62
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Maths help....Again...exp? Brill, many thanks, had the scientific already but didn't know there were more keys, thought it was just exp not ex as well, anyways just done that exercise for 0.03334 and it returns the correct answer, eureka! Next, a step by step instruction for the procedure to do the calc using the original formula, can you help with that? Original formula...Vr=(Vp-0.7)(1-exp(-T/CR)) I can do Vp-0.7 no problem, I can also do T/CR no problem, the answer should be 0.47 volts or thereabout using that formula with the following inputs...Vp=15 volts...T=0.01667 secs...R=5,000 ohms...C=100uF Lawrence.

9th Apr 2019, 11:10 pm	#64
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Maths help....Again...exp? I think I've figured it out now using the Windows 10 scientific calc now that I've found the ex function and I find it faster using the formula derived by GJ from my original alternative method, is that coincidence or is there a faster way using the original formula? Lawrence.