whitten@kuhub.cc.ukans.edu (03/16/90)
Could anyone tell me what the most efficient way to convert +1 to -1 audio signals to 0 to +5 volts? The analog to digital IC I'm using will only work on zero to five, and everything I've tried so far has had pretty crummy results. (Lots of noise and the likes.) Thanks, Chris Chris Whittenburg University of Kansas WHITTEN@KUHUB.CC.UKANS.EDU
richm@amc-gw.amc.com (Rich Moran) (03/20/90)
In article <22500.260029fb@kuhub.cc.ukans.edu> whitten@kuhub.cc.ukans.edu writes: > >Could anyone tell me what the most efficient way to convert +1 to -1 >audio signals to 0 to +5 volts? The analog to digital IC I'm using >will only work on zero to five, and everything I've tried so far has >had pretty crummy results. (Lots of noise and the likes.) > >Thanks, >Chris > >Chris Whittenburg >University of Kansas >WHITTEN@KUHUB.CC.UKANS.EDU +5V _ | > >10K 1uF + > |\ -||--o | \ U1a | > VR1 | \ | ><------|+ \ | > | \ + 10uF | | | >------o-------||--i | | | / | | | | --|- / | | | > | | / | V | >10K | | / | gnd | > | |/ | |----o | | | !-------------o----o V | | gnd | | | > | > 620 | > |\ U1b 10uF N.P. | | | \ Sig in >----||--------------o-------|+ \ | | \ | | \ > | >-------o-------->> Sig out >10K | / | > | / | | --------|- / > | | | / >50k | | |/ > | v | ---^^^^------------------------- VR2 Here's something to try. This assumes that you only have the single +5V supply available. U1 is a reasonable quality multiple op amp capable of swinging its output to the 0 and 5-volt rails (i.e., CMOS; eg., National LMC660). U1a provides a 1/2 VCC reference by dividing the +5V input. This reference should be adjusted to precisely 1/2 VCC using 1K-ohm potentiometer VR1. The input signal is coupled through a non-polarized capacitor, and referenced to the 1/2VCC rail via a 620-ohm resistor (note that this gives you a ~620-ohm input impedance). U1b is a non-inverting amplifier with a gain of approximately 5, again referenced to the 1/2VCC rail. A gain of 5 allows a typical 1V pk-pk audio line-level signal to be adjusted to the 0-5V range. The gain of this stage can be precisely adjusted using 5k-ohm potentiometer VR2. Rich -- ============================================= Rich Moran richm@amc.com =============================================
twheeler@jarthur.Claremont.EDU (Theodore Wheeler) (03/20/90)
Have you tried a clamping circuit that clamps -1 to 0v, therefore, +1 to 2v?
However, this won't clamp +1 to +5v.
Good luck.
T.J.tomb@hplsla.HP.COM (Tom Bruhns) (03/21/90)
>Could anyone tell me what the most efficient way to convert +1 to -1 >audio signals to 0 to +5 volts? The analog to digital IC I'm using >will only work on zero to five, and everything I've tried so far has >had pretty crummy results. (Lots of noise and the likes.) Lots of noise? Keep leads short and power supplies clean. As far as about the simplest circuit for doing this, try one op amp and four resistors. I don't like to draw with ascii characters, so: R1: from input sig to inverting opamp input. R2: from opamp output to inverting opamp input. (Take output from opamp output, of course.) R3: from some positive reference supply (say +5 volts) to opamp non-inverting input. R4: from opamp non-inverting input to ground/common. R1 and R2 set a signal gain of 2.5, to get from 2 volt input range to a 5 volt output range. Pick R1, say, 10K ohms. Pick R2 = 2.5* R1; 24Kohms is probably fine, maybe even 22K ohms. R3 and R4 set the bias on the non-inverting input to the opamp. Pick them so that +1 volt in and 0 volts out, voltage-divided across R1-R2, gives the same voltage as R3-R4 divide down to the non-inverting input. Probably best to bypass the non- inverting input to ground with a capacitor; let R4 be 10K ohms, and try a bypass of somewhere around 27 to 100 microfarads (non-critical ;-). e.g., 5V * R4/(R3+R4) = 1V * R2/(R1+R2) Pick R4 as a convenient value, say 10K ohms, since the above will give only a ratio of R3:R4. If R2 == 2.5*R1, then this works out to R4/(R3+R4) = .142 if I did my math right, and R4=10K ---> R3=60K -- 62K is a close 5% value... Op amp should be capable of operation at about 0.5 volts input, and its output should be able to swing the full 0-5 volts. This can be satisfied with some single-supply amps, and most any amp running on +/- 15 volt supplies. Op amp noise shouldn't be a problem at these signal levels unless you have a really poor opamp...or very high accuracy digitization following.
richm@amc-gw.amc.com (Rich Moran) (03/22/90)
In article <5170078@hplsla.HP.COM> tomb@hplsla.HP.COM (Tom Bruhns) writes: }}Could anyone tell me what the most efficient way to convert +1 to -1 }}audio signals to 0 to +5 volts? The analog to digital IC I'm using }}will only work on zero to five, and everything I've tried so far has }}had pretty crummy results. (Lots of noise and the likes.) } } }Lots of noise? Keep leads short and power supplies clean. As }far as about the simplest circuit for doing this, try one op }amp and four resistors. I don't like to draw with ascii characters, }so: } }R1: from input sig to inverting opamp input. }R2: from opamp output to inverting opamp input. } (Take output from opamp output, of course.) }R3: from some positive reference supply (say +5 volts) } to opamp non-inverting input. }R4: from opamp non-inverting input to ground/common. } }R1 and R2 set a signal gain of 2.5, to get from 2 volt input } range to a 5 volt output range. Pick R1, say, 10K ohms. Pick } R2 = 2.5* R1; 24Kohms is probably fine, maybe even 22K ohms. } }R3 and R4 set the bias on the non-inverting input to the opamp. } Pick them so that +1 volt in and 0 volts out, voltage-divided } across R1-R2, gives the same voltage as R3-R4 divide down to } the non-inverting input. Probably best to bypass the non- } inverting input to ground with a capacitor; let R4 be 10K ohms, } and try a bypass of somewhere around 27 to 100 microfarads } (non-critical ;-). } } e.g., 5V * R4/(R3+R4) = 1V * R2/(R1+R2) } Pick R4 as a convenient value, say 10K ohms, since the above } will give only a ratio of R3:R4. If R2 == 2.5*R1, then } this works out to R4/(R3+R4) = .142 if I did my math } right, and R4=10K ---> R3=60K -- 62K is a close 5% value... } This circuit works slick, except that the audio signal is inverted at the output. -- ============================================= Rich Moran richm@amc.com =============================================