Need help? HT9170 OUTPUT DV PIN 15

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cybertron

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Hi all

I am using the 9170 dtmf decoder chip.

What i need to know? If I use 5.0V or 3.6V to power this chip.

1.What would the voltage and the output current be on pin 15 with a power supply of 5.0V.
With or with a valid tone

2. What would the voltage and the output current be on pin 15 with a power supply 3.6V.
With or with out a valid tone

Also there will be an NPN switching transistor BC549 to turn on an LED for detecting a Valid
tone on the output of pin 15 . If there IS no tone the LED stay's off.
If there is a Valid tone the current turns on the transistor then turns on the LED.
The LED is a froward voltage of 1.6V for it to turn on.Using a 470 resisto

https://www.digikey.com/product-detail/en/BC549BTF/BC549BTFCT-ND/4744184 DATASHEET-LINK?

What value of resistor would I use for the Base of the transistor. for 5.0V power supply

What value of resistor would I use for the Base of the transistor. for 3.6V power supply
 

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  • 9170v111.pdf
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cybertron said:
Hi all

I am using the 9170 dtmf decoder chip.
What i need to know? If I use 5.0V or 3.6V to power this chip.
Click to expand...


Spec says use 2.5~5.5V wide range for Vcc.Use Ohm's Law
1.What would the voltage and the output current be on pin 15 with a power supply of Vcc?

With or without a valid tone
Click to expand...

CMOS OUT means Vcc="1" or 0V ="0"
Pin 15=DV="1"= received Valid Dualtone


This IC CMOS out sinks "0" more than sources "1", which means higher internal drive resistance.

IOH=-0.4mA (min) at VOH=5V-0.5V so source Rs internal=0.5V/0.4mA = 1250 Ohm. (Max)

When choosing Rb subtract this from required value.

If using High Bright (HB) Red LED then Vf=2V
- then (Vcc-2V)/If =R determines current from output.

e.g. Using 5mA (max) will work , without much drain or heat and using HB LED gives bright indication.

When using any transistor as switch, assume Ic/Ib=10 , unless special parts which use Ic/Ib=50 ( ultra low Vce ), thus 0.5 mA base current.

-thus for Vcc with 0.5 =Vce drop and 1.7 or 2V LED , Rc is calc. Using Ohms Law for across series R.
- same for base current , subtract Vbe then Ohms Law on base current including driver impedance of 1250 Ohms , worst case.

Here are some 5mm RED LEDs with high [mcd] brightness. Note deep red is 1.7V and lighter but brighter Red is 2V using AlInGaAs.

Now you have all the info to calc. your own answers.
 

Thank for your help sunnyskyguy. BuT do not know where to start with all that info
you given me.

All's I needed was what the current output on the 9170 chip would be
with a 5V power supply and a valid tone on the output. to turn on transistor.
And what would the Rb resistor on the transistor base be. as switch.
and the resistor for LED connected to the collector C.


Can to may it much more easier or an example.If not? That's OK.

Could someone else help me.
 
Last edited:

The datasheet says that with a 5V supply the output high will be +4.5V when the output current is 0.4mA or more.
The base of an NPN transistor is about 0.7V when it is turned on so the voltage across a base resistor for a transistor LED driver is 4.5V - 0.7V= 3.8V.
The minimum output current is 0.4mA so ohm's Law calculates the base resistor to be 3.8V/0.4mA= 9.5k which is not a standard value. Use 10k.


The ultra bright LEDs listed have an extremely narrow light beam like a laser so they are not suitable as an indicator. Use a wide angle LED instead but it might need 10mA of current.
Some BCxxx European transistors saturate fairly well when their base current is 1/20th the collector current.

If you have a 1.8V red LED and the saturation voltage loss of the transistor is 0.1V then with a 5V supply the resistor value in series with the LED to produce 10mA of current is (5V - 1.8V - 0.1V)/10mA= 310 ohms which is not a standard value. Use 330 ohms.
 

I tried to let him solve LED R directly driven from CMOS 9170V11 pin 15.

@IOH=-0.4mA (min) at VOH=5V-0.5V
so source Rs internal=0.5V/0.4mA = ESR
@IOH (min)=-0.4mA ESR = 1250 Ohm (Max)
@ IOH(typ) =-0.8mA , ESR= 620 Ohms (typ) <added>
Click to expand...

The solution could be direct drive from 3.6V on high side for (3.6-2V)/1250 =1.2mA min, 2mA typ. For 5 V, (5-2)/1250=2.4mA min 5mA typ. using an efficient wide angle LED. add 620 Ohm in series for less variation for production.

The Iv, intensity is proportional to If, current, but indicators using HB chemistry (AlGaAs) @2V compared to 1.7V older deep red (GaAs) for same mcd. (millicandella) 100mcd is adequate. 10000mcd is blinding up close.

My previous link showed hundreds to choose from including 8 deg to 200 deg. designer's choice using filter menu.

Here are some 5mm RED LEDs with high [mcd] brightness. Note deep red is 1.7V and lighter but brighter Red is 2V using AlGaAs.
Click to expand...

A good example of a 5mm 60 deg 1.7 V deep Red 1000mcd @20mA, low cost, $0.09 @1k is this part. When driven @ 2mA generates 100 mcd which is minimal adequate for indicators. some oldest types were only 2mcd.
 

Don't you want an indicator LED to be visible over a wide angle that is almost 80 degrees for each side? Then you want a 160 degrees viewing angle, not just 60 degrees that is visible at only up to 30 degrees off axis. Then since it is focussed less it will be dimmer.
 

Hi

I like to thank all who posted there comments.

What I need was the example you given me to Under stand this stuff.

Audio guru? This is what I done already I've use 10K on the base Rb
And I used 470ohms for the LED on the collector side and it did not work at all.
the LED that I used is 60degree angle 30degrees for each side of the viewing angle
this is not the problem.also the forward voltage on my LED is 1.6V not 1.7 or 1.8v.
this also is no problem.

If i used those values why doesn't the transistor turn on when there's a value tone
I tryed it with out the transistor on the out put of pin 15 and it worked every time I press a key on
the online dtmf generator. I used the circuit in the datasheet for my circuit.
 

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  • DTMF DECODER.PNG
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When the output pin 15 goes high to about +4.5V and the base-emitter of the transistor has a 0.7V drop then the 10k resistor feeds a base current of (4.5V - 0.7V)/10k= 0.38mA. Then the collector current is 3.8mA with a low saturation voltage of 0.1V. The collector current is higher if a resistor in series with the LED allows it but then the saturation voltage is higher.

Maybe the saturation voltage is 0.5v then the current in the LED is (5V - 1.6V - 0.5V)/470 ohms= 6.2mA which is fairly bright.
Maybe you have the LED wires backwards.
 

Maybe you have the wrong orientation for BCE, ECB, BEC? Check both PN junctions with an ohmmeter if Q1 is still OK. Normally + on Red DMM to base the - to either E or C conducts or 0.65 in diode test mode.

But as I proved, direct attach to this IC works with internal RdsOn!
 

The datasheet for the BC549B shows which pins are CBE because it is European. American transistors like the 2N3904 have the pins reversed from the Europeans and is EBC.
An LED does not light when it is connected backwards.
 

Got it working.

Now i would like to use an electret microphone connect to the input.To pick up the dtmf tone
sounds from across the room about 12-14ft. What capsule microphone should i get.can you recommend
one from ebay or digikey.com. What resistor will i need to bias the mic to turn it on.How much gain
would I need to set on the 9170 to pick up the tone sounds from across the room.Any ideas.do i need a capacitor on the input for DC blocking.Not sure how or what value to use for that. Please make this simple as possible to understand. appreciate you input. You can use the circuit i post to make change for Mic input connection. or example..
 

You would need an electret or magnetic mic with a cardioid sensitivity pattern. Most electet mics are "noise cancelling" meaning the diaphram is open on the back so,only near field sound pressure is detected. some desktop mics are even like this. you could block the rear vent and choose 10k for the gain and bias setting of any FET buffered electret $1 mic but you must use a differential amp,to reject stray hum from high E field,power noise and CM choke. Then use the standard AC coupled OP Amp with high gain to,boost a 5mV signal to 1V or so using the Decoder chip with a gain of 200.

https://en.m.wikipedia.org/wiki/Electret_microphone

Vdc range from 3 to 5V might work, for a small signal input from external power from your box. mic voltage should around 0.5V below V+, R pullup can be experimented for max gain and smallest drop DC voltage. This becomes your source impedance in the OA negative feedback , so a gain of 200 requires 2M feedback with .10k pullup.
 

SunnySkyguy said:
Most electet mics are "noise cancelling" meaning the diaphram is open on the back so,only near field sound pressure is detected.
Click to expand...
I disagree.
Most electret mics have a sealed back so that they are Omni-Directional (they pickup sounds from almost all directions).

Cybertron,
If you buy a mic from ebay then it will probably have no datasheet and will have very poor quality. Buy one from Digikey.
Pickup across a room?? From what?? A speakerphone?
The pickup will consist of background noise and echoes. The echoes cause delays then some frequencies are cancelled. Then the touch tones will be so messed up that the decoder might not decode them.

Our hearing is in stereo so that our brain can cancel background noises and echoes. Plug one ear to hear it.
 

This is good info at best.
I have no experience in building an audio amp or how to filter out noise and echoes
from my computers speakerphone.or any sound source.

I need to buy a electret mic or magnetic mic. I know what an electret is? I don't know or what
or how to use an magnetic mic. Or where to purchase one.
It seems that I may need a Omni-directional type of mic capulse, which are lease expensive then
to buy a Microphone pre-made.

I would need a schematic from both of you at best to even try to make this work with all components so I could buy them from digikey.com.Oh and i do not want to be making any chokes,inductor's,etc. must buy them.

My voltage range would be 3.6 to 5.0v and battery powered.and to have the circuit to use low current becuase of running on batteries. Can either of you provide a simple circuit that would work for me to connect to the input of the 9170. I like to try your concept sunnyskyguy But? I would need a schematic to even try
to get it working. If you want tr from audio guru. Remember this I'm a tinker in electronics not an engineer like you guys.
If i new how to perpare and design an audio amp I might not be here for the need of your help.
 
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Background noise and echoes have the same frequencies as the touch tone signals so they cannot be filtered out.
Maybe you can use two directional (expensive) mics pointing in different directions and two preamps for them then add their signals. Noise and echoes will be different in each mic so they will not add, but might cancel a little. The touch tone signals will be the same in each mic so they will add.

My electret mic preamp is powered by a 9V battery.
Texas Instruments sells an IC preamp designed to be placed inside an electret mic so it is extremely small (1.2mm square, its four solder pads are o.5mm apart). Its minimum supply is 2.0V and its current is typically only 60uA. But its gain is a max of only about 17.7 times, you will need two in series. Look at the datasheet for the LMV1032.
 

Can't buy expensive microphones so that would not work for me.

Your preamp is powered with 9V battery. Wouldn't work for me.Using 5V supply.Unless
I use X2 9V batteries in parallel and a 7805 regulator that would give me enough current and voltage.
But? Can your preamp pick-up the tones from computer speakers or any other sound source 10-14
feet away in a room. ''Post'' your preamp.

I like the Texas Instruments IC preamp design to be placed inside an electret mic But? the side.
How would i even solider the two chips.Then place them inside the small electret mic then connect it all together for this to work.And WHICH electret mic do I use.
There are three dbi types for the preamps 6db,15db and 25db which one did you suggest to use.
There very small.

Your preamp is powered with 9V battery. Wouldn't work for me.Using 5V supply.Unless
I use X2 m9v batteries in parallel and a 7805 regulator that would give me enough current and voltage.
But? Can your preap pick-up the tones from a computer speakers or any other sound source 10-14
feet away in a room.
 

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  • snas233g-286183 Datasheet.pdf
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Last edited:

My preamp uses an audio opamp that has a minimum supply of 7V so it works fine when powered from a 9V battery. it is a standard opamp circuit that has its gain determined by the ratio of two resistors. If the resistance of one resistor is increased then the gain is increased.

Texas Instruments has 49 audio opamps. Many will work when powered from 5V. Look at the datasheet of the TL971 single, TL972 dual and TL974 quad audio opamp. https://www.ti.com/lit/ds/symlink/tl971.pdf
Its minimum supply is 2.7V and its maximum supply is 12V so 5V is fine. Its output current is low but it can drive a 10k ohms load. It will work in my modified preamp circuit attached to this reply.

Why do you need to pickup touch tones as far away as 14 feet away in a room? The tones will produce echoes and there will probably be background sounds. Then the HT9170 probably will not work.
 

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  • mic preamp for weak touch tones.png
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Looks like TI latest LMV1032-25 3-wire or LMV1012-25 2-wire product offering, 5V in highest 25 dB gain electret mics is the way to go forward. Although you may need another 25 dB gain design built-in the free Op Amp in the decoder DTMF IC. 0.37$@1k

A proper design would factor path and fading losses to determine how much directional mic gain needs to be added with either parabolic reflector and or active ambient noise cancellation.

DTMF chip normally expects high level and high SNR, so some research needed to determine effects on low SNR.
 

Looks like TI latest LMV1032-25 3-wire or LMV1012-25 2-wire product offering, 5V in highest 25 dB gain electret mics is the way to go forward. Although you may need another 25 dB gain design built-in the free Op Amp in the decoder DTMF IC. 0.37$@1k
Click to expand...
Sunnyskyguy

As audioguru suggested these type of preamps. They look like it could work.But? like I said. How would I open up an electret capsule Mic solder two 1,2mm size in series then close the Mic back up.Who knows if they will work.after opening them up. Unless they come already build into the mic.Then I could work with that. Are you telling me they already build into a mic.
The two that you posted here. LMV1032-25 3-wire or LMV1012-25 2-wire.
 

You do not need to open the electret microphone. The extremely tiny preamp IC can be mounted anywhere nearby and connected with tiny wires.
It is too small to solder, usually a robot does it. I do not know about any electret mic that already has this tiny preamp IC inside it.
 

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