Link500
Posts: 5
Joined: Wed Aug 01, 2018 3:42 am

what to do with an old police scanner.

Thu Aug 16, 2018 12:53 am

Ok so this is gonna probably be a really weird question but...

Basically i found an old RadioShack police scanner of my grandfathers, like really old...so naturally i took the thing apart cuz i was curious about the insides of it...

Now I’m curious if there’s anything I could use off of this for anything on a pi project? There’s the most obvious which is using just the speaker for something, but it’s got a lot of other things like switches and dials and lights, and since it was made in the 70s the board has everything hardwired up so I’d have plenty of spare wire on to use.

Obviously I don’t know a lot of stuff about electronics other than how to use em, but that’s one of the reasons why i got a pi in the first place. So I’m just curious if anyone knows of any simple projects I could use this with in conjunction with the pi that would be both a good learning experience programming wise and hardware wise.

EDIT: I’m assuming I’d probably need some sort of analog to digital converter for many of the parts off this right?

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karrika
Posts: 1045
Joined: Mon Oct 19, 2015 6:21 am
Location: Finland

Re: Not sure where else to ask this....

Thu Aug 16, 2018 8:39 am

A Pi has audio out. But you may need a little amplification to feed the sound to the speakers. Buttons can be connected to GPIO pins for detecting when you press them. The dials could be read with some electronics magic. LED's can be controlled by a Pi.

The question remains... What should it become? A sonic screwdriver for your time travels?

There is a lot of beginners projects in MagPi and on the net. The easiest project could be to just create sounds and flash leds when you push the buttons. This would be a good starting project perhaps...

Heater
Posts: 9700
Joined: Tue Jul 17, 2012 3:02 pm

Re: Not sure where else to ask this....

Thu Aug 16, 2018 9:11 am

Any chance you could post a picture of this relic, inside and out?

I'm all for taking things apart and trying to get some idea as to how they work. Or even just what the parts are in there. On rare occasions I have even managed to repair something.

First step is to identify all the components. Google is great for that now a days.

wolf.z
Posts: 49
Joined: Thu Dec 24, 2015 8:34 pm

Re: Not sure where else to ask this....

Thu Aug 16, 2018 9:27 am

Considering what a radio scanner is intended for you might build an analogue to streaming-for-whatever setup. However, I am neither aware, whether the police radio communication in your country is already digitized nor it is legal to scan this kind of communication.
Assuming, you reside in the US: To my knowledge listening to police communication in US is legal. However, I think, things already went digital so you probably won't have a chance of simply digitizing whatever you analogue scanner outputs.
Possibly you might get engaged in doing some software defined radio stuff for picking up digital communication and decoding that in software. However, if no one would have done this before, I see no room for beginners to get engaged.
Bottom line, better stay with what Karrika suggested.

scotty101
Posts: 3031
Joined: Fri Jun 08, 2012 6:03 pm

Re: Not sure where else to ask this....

Thu Aug 16, 2018 10:47 am

If this device is totally broken and beyond repair, I'd consider turning this in to a Software Defined Radio "scanner".

Strip out the contents and replace with a Pi and a USB SDR module (many TV modules can be used) and install some software to pick up and decode radio frequencies.
Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

Link500
Posts: 5
Joined: Wed Aug 01, 2018 3:42 am

Re: Not sure where else to ask this....

Thu Aug 16, 2018 7:52 pm

scotty101 wrote:
Thu Aug 16, 2018 10:47 am
If this device is totally broken and beyond repair, I'd consider turning this in to a Software Defined Radio "scanner".

Strip out the contents and replace with a Pi and a USB SDR module (many TV modules can be used) and install some software to pick up and decode radio frequencies.
It’s not broken so much as it just has no real use for its original function anymore, like wolf said, far as I know everything is digitized now, so when I turn this on I won’t pick up anything as it uses the old scanner crystals tuned to a specific frequency. So I figured why not try and anything off it to make something actually functional again?

Here’s a few pictures of it.


https://ibb.co/dzEmhe
https://ibb.co/cG6ovz
https://ibb.co/jBXBFz
https://ibb.co/cZEDTK
https://ibb.co/jtFRhe

LTolledo
Posts: 530
Joined: Sat Mar 17, 2018 7:29 am

Re: what to do with an old police scanner.

Sat Aug 18, 2018 11:28 am

Nice pics of the "relic" you have there!

If it were me, I'd take everything out of the case, carefully, I'd save the speaker, the LEDs and some knob, the case of course!
I'd probably save the crystals as well.

Turn the unit to an RPi powered music streamer with LED VU meter display (thus the LEDs)
for that you might need the following

1. Raspberry Pi 3 model B (an alternate will be a Raspberry Pi Zero W)
2. USB sound card (cheapo ones will do fine). An alternate will be a Pimoroni pHAT DAC
3. 5V mono amplifier board (probably around 3W, using PAM8403 chips)
4. DIY VU meter using LM3914/3915 (to connect to LEDs on the panel)
5. 5v 2.5 PSU
6. microSD card 8GB minimum
7. audio app like Volumio (or Rune or moOde, etc)
8. a couple of wires
9. some soldering skills perhaps....(actually definitely!)

its just one suggestion, others might give you more exciting ideas....
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

Link500
Posts: 5
Joined: Wed Aug 01, 2018 3:42 am

Re: what to do with an old police scanner.

Wed Aug 22, 2018 9:56 pm

LTolledo wrote:
Sat Aug 18, 2018 11:28 am
Nice pics of the "relic" you have there!

If it were me, I'd take everything out of the case, carefully, I'd save the speaker, the LEDs and some knob, the case of course!
I'd probably save the crystals as well.

Turn the unit to an RPi powered music streamer with LED VU meter display (thus the LEDs)
for that you might need the following

1. Raspberry Pi 3 model B (an alternate will be a Raspberry Pi Zero W)
2. USB sound card (cheapo ones will do fine). An alternate will be a Pimoroni pHAT DAC
3. 5V mono amplifier board (probably around 3W, using PAM8403 chips)
4. DIY VU meter using LM3914/3915 (to connect to LEDs on the panel)
5. 5v 2.5 PSU
6. microSD card 8GB minimum
7. audio app like Volumio (or Rune or moOde, etc)
8. a couple of wires
9. some soldering skills perhaps....(actually definitely!)

its just one suggestion, others might give you more exciting ideas....
I think I might try this. I do have a few more questions...


is there anyway to set it up as not only a music streaming device, but able to switch to a normal radio using an antenna with say a button press?

..outta curiosity why keep the crystals? What else could I use them for?


Sorry if these seem like crazy questions, I know I could just get another normal radio, but I’m kinda curious if something like this could even be possible using the pi

LTolledo
Posts: 530
Joined: Sat Mar 17, 2018 7:29 am

Re: what to do with an old police scanner.

Fri Aug 24, 2018 9:59 am

Link500 wrote: is there anyway to set it up as not only a music streaming device, but able to switch to a normal radio using an antenna with say a button press?
Yes this is possible, but you will have to install in an FM Tuner module which will act as a second audio source.
while you're at it better add a third sound source called "AUX"

Thus your sound sources will be
a. Raspberry Pi (Zero W) with pimoroni pHAT DAC, Volumio music app
b. FM tuner module
c. AUX input (from RCA jack at the back)
you may add one more if you like.

the audio outputs of the three will be connected to a selector switch (there are digital selector switch available) or re-wire the push button switches in front panel to act as source selector switch.

the output of the selector switch will be connected to the audio input section of the amplifier.

the amplifier output will be connected to the speaker.

Note: you may also need to install a "Ground Loop Isolator/Noise Filter" between the selector sw and the amplifier. To get rid of the awful "HuMmmm", "Pops" and "Crackles" associated with connecting audio sources from 1 power source. Its not that expensive. Cost me less than USD1 for one unit.

FYI: With the volumio system on the RPi, you may be able to tune in to internet radio stations (there are quite a lot to choose from)

Link500 wrote: ..outta curiosity why keep the crystals? What else could I use them for?
That is if it were me.... I'd keep the crystals, maybe I might have use for those in future projects...
but if you think you wont have any need for those crystals, then you may get rid (or maybe sell off) those as well.

Looking forward to your progress in your build....have fun!
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

wolf.z
Posts: 49
Joined: Thu Dec 24, 2015 8:34 pm

Re: what to do with an old police scanner.

Fri Aug 24, 2018 6:48 pm

LTolledo wrote:
Fri Aug 24, 2018 9:59 am
...you will have to install in an FM Tuner module which will act as a second audio source.
while you're at it better add a third sound source called "AUX"
...
c. AUX input (from RCA jack at the back)
you may add one more if you like.
...
Looking forward to your progress in your build....have fun!
LTolledo definitely lit the fire: "Add more if you like". Throw away my latest post concerning police communication. Why not add a software defined radio (SDR) toolkit after having added the fm tuner module? Like GNU radio or better more user-ready SDR apps? With this, a higly single-band focused scanner from the 70s might get the physical basis for the scanner idea of this millenium? There is not only solutions for FM reception existing. Thre are solutions for even very special radio services including aviation, marine, scientific, amateur radio,
Add more... as LTolledo said.

Link500
Posts: 5
Joined: Wed Aug 01, 2018 3:42 am

Re: what to do with an old police scanner.

Wed Aug 29, 2018 6:47 pm

So a bit of an update...I’ve finally gotten around to disassembling things off the scanner... turns out the bulbs aren’t led, they appear to be tiny incandescent ones. Idk how much that changes things but figure I should mention it. I made sure to take photos of everything as i was doing it, so i know which wires are for what especially on things like the potentiometers.

I’m gonna wait to order the parts since my vacation staycation is next month so I’m gonna try to set it up to where I’ll be home when everything arrives, sadly my neighborhood isn’t the most trustworthy and folks have had packages stolen before around it, so I’d rather be safe than sorry....that and I’ll have more time to decide on which parts to order

On the bulbs, do I need resistors with em? So far everywhere i look online it stresses to use resistors for the pi for leds. Now knowing that these aren’t LED, I’m wondering if it’s even more important to use them, or would the pi still even power them? I also have the old resistors on the scanner that can possibly be reused, From what it looks like if I traced em back to the bulbs correctly, based on the color code they seem to be 10k resistors.

Also I know the pHAT dac is digital to analog, but would I also need an adc as well?


Sorry for so many odd questions, Again this is my first project on this so I’m a complete beginner, but figure i gotta learn somehow.

Edit: so as far as some parts I’m ordering...

The pimoroni pHAT dac
The Adafruit mono 2.5 class d audio amplifier.

The amp should work, others though like the fm tuner module, I’m not sure what the best one to get would be for what I’m doing, or if I’ll need anything else with it, as the few I’ve seen seem to be for Arduino (would they still work?) Trying to also have it so the antenna can fit from the old spot as well..

I’ve already got the psu from pi, and was gonna run the cord through the back where the original was for the scanner. For the VU meter seeing as the lights aren’t LED like I originally thought, idk if the same chip would work.

LTolledo
Posts: 530
Joined: Sat Mar 17, 2018 7:29 am

Re: what to do with an old police scanner.

Wed Aug 29, 2018 10:29 pm

Hi there!

Am glad you took my suggestion and will try to assist you as much as I can.

Before assembling everything into the scanner box test each module one by one.

the modules will be
Module 1: RPi Module
  • Raspberry Pi Zero W
    Pimoroni pHAT DAC
    5v 1A PSU
    8GB microSD
    music App (lets try Volumio as its the one that I have)
though not needed, I recommend installing a small heatsink, 5mm in height, to the RPiZW's main chip.
a 5V 1A USB PSU and 2.0A microSUB charging cable from a dollar store is what I use.

Module 2: Amplifier Module
  • Adafruit Mono amplifier
    PSU for the Mono amplifier (I assume its also 5V powered)
    Speaker (the one from the scanner)
if you choose to use separate PSU for the mono amp then we might not need the Ground Loop Isolator

Module 3: Audio Selector Module
  • RCA jacks (3 for input, 1 for output)
    push button switches (from the scanner, number depending on input count)
    shielded audio cable
here you may need to temporarily connect each one
if you plan to add additional audio input source later, just add RCA jacks and push button switches.

Module 4: DIY VU Meter Module
  • I'll refer you to the link that I used to make my VU meter
    https://circuitdigest.com/electronic-ci ... ing-lm3914
    we wont use the mic, R2 and R3 in the diagram, and replace C3 with 0.1uF
    I'll send my final diagram later.
    As the panel lights being not LEDs we may still be able to use it if you can trace the voltage rating of the bulbs, or replace those with similar sized LEDs
    there are rectangular LEDs like thesehttps://www.amazon.com/200pcs-2x5x7mm-Rectangle ... ngular+LED
    Or you can get a kit from your favorite online shopping/electronics shop
Module 5: FM receiver Module
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

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