Providing Clean Sine Wave Input for the Emic Text to Speech Module
latigerlilly
Posts: 114
Hi guys,
The Parallax Emic Text to Speech (TTS) module has a schematic in the manual that says I'll need resistors, capacitors and variable resistors in order to set-up a device that will provide a clean sine wave to the audio input of the TTS:
www.parallax.com/dl/docs/prod/audiovis/EmicModules.pdf
Are the following parts O.K. to use?
1. Radio Shack 272-1069 PC Mount 0.1 uF, 50 VDC, +/- 10% capacitor OR
Radio Shack 272-1053 Metallized Polyester Film 0.1 uF, 250 VDC, +/- 10% capacitor
I am guessing that the 272-1053 is O.K. to use since the Basic Stamp is 5 VDC but this capacitor is rated for 250 VDC, so it has plenty of spare capacity to handle the voltage of the Basic Stamp. Is this correct?
2. Radio Shack 271-1721 Audio Taper Potentiometer, 50 k-ohm, 0.5 watt, 20% tolerance
Radio Shack 274-402 Knob for Potentiometer
The EMIC has s 300 mW capacity so a 0.5 watt pot should be alright. I will connect just two leads of the pot to use it like a variable capacitor. I will just have to try the knob to see if it will fit the potentiometer. Will this setup be O.K.?
3. Radio Shack resistors
0.25 watt resistors are fine or do I have to use 0.5 watt resistors here? I want to use a combination of resistors (some 0.25 wattt and some 0.5 watt) to arrive at the value of 47 k-ohm. For example four 10 k-ohm 0.5 watt resistors and seven 1 k-ohm 0.25 watt resistors in series. This should be O.K.?
Thanks,
Lilly.
P.S. I am using the PDB with a BS2P40. By the way, I a goofed up and somehow accidentally posted this twice (oops)....
Post Edited (latigerlilly) : 2/25/2007 6:00:29 PM GMT
The Parallax Emic Text to Speech (TTS) module has a schematic in the manual that says I'll need resistors, capacitors and variable resistors in order to set-up a device that will provide a clean sine wave to the audio input of the TTS:
www.parallax.com/dl/docs/prod/audiovis/EmicModules.pdf
Are the following parts O.K. to use?
1. Radio Shack 272-1069 PC Mount 0.1 uF, 50 VDC, +/- 10% capacitor OR
Radio Shack 272-1053 Metallized Polyester Film 0.1 uF, 250 VDC, +/- 10% capacitor
I am guessing that the 272-1053 is O.K. to use since the Basic Stamp is 5 VDC but this capacitor is rated for 250 VDC, so it has plenty of spare capacity to handle the voltage of the Basic Stamp. Is this correct?
2. Radio Shack 271-1721 Audio Taper Potentiometer, 50 k-ohm, 0.5 watt, 20% tolerance
Radio Shack 274-402 Knob for Potentiometer
The EMIC has s 300 mW capacity so a 0.5 watt pot should be alright. I will connect just two leads of the pot to use it like a variable capacitor. I will just have to try the knob to see if it will fit the potentiometer. Will this setup be O.K.?
3. Radio Shack resistors
0.25 watt resistors are fine or do I have to use 0.5 watt resistors here? I want to use a combination of resistors (some 0.25 wattt and some 0.5 watt) to arrive at the value of 47 k-ohm. For example four 10 k-ohm 0.5 watt resistors and seven 1 k-ohm 0.25 watt resistors in series. This should be O.K.?
Thanks,
Lilly.
P.S. I am using the PDB with a BS2P40. By the way, I a goofed up and somehow accidentally posted this twice (oops)....
Post Edited (latigerlilly) : 2/25/2007 6:00:29 PM GMT
Comments
1) Either one will work fine
2) Personally I would use a linear taper and a 10K pot. The "Wattage" should be determined by the I/O capacity of the stamp. Since it can only source or sink roughly 20-25mA, at 5V that only
amounts to 125mW MAX with a dead short. Basically look at your resistors with reference to your capacitors. At times (frequency dependent) a capacitor will look like a short. The worst case
scenario would be 1K to ground directly off of P7. That's only 25mW (P = V^2 / R). The best case scenario would be 424uW (P = V^2 / Rtotal)
Reference page 17 of the pdf
Connecting a resistor in series with a capacitor does not make it a variable capacitor. A leaky capacitor yes, a variable capacitor no.
You can still use just two leads of a pot by connecting one to ground, and the other to the 47k resistor. The 0.1uF capacitor going to the Emic would connect to the node between the 47K resistor and the pot.
3) Refering to #2, you could go as low as 1/40th watt resistors and still be just fine. If you want to use a combination of resistors that's fine also, but 47K is a standard resistor value.
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 2/25/2007 6:57:40 PM GMT