Difference between revisions of "Frequency Counter"
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** [https://owenduffy.net/blog/?p=11386 DL4YHF 50MHz counter on a Chinese TB-244746 PCB] | ** [https://owenduffy.net/blog/?p=11386 DL4YHF 50MHz counter on a Chinese TB-244746 PCB] | ||
* Frequency range: 1 Hz-50 MHz | * Frequency range: 1 Hz-50 MHz | ||
| − | * Crystal Test Range: 4 MHz-48 MHz | + | * Crystal Test Range: 4 MHz-48 MHz |
| + | ** Mods to replace crystal checker with sensitive pre-amp | ||
* PCB size：8*5.3cm | * PCB size：8*5.3cm | ||
** Fits in 100 x 60 x 25 mm enclosure | ** Fits in 100 x 60 x 25 mm enclosure | ||
* Source - [https://www.aliexpress.com/item/4001262793719.html?spm=a2g0o.productlist.0.0.a6a57b558PTLGq&algo_pvid=77bddd5c-6ae2-4082-8837-73945f792fae&algo_expid=77bddd5c-6ae2-4082-8837-73945f792fae-0&btsid=0bb0622f16000865130548256e846c&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ AliExpress Frequency Counter] - Very inexpensive | * Source - [https://www.aliexpress.com/item/4001262793719.html?spm=a2g0o.productlist.0.0.a6a57b558PTLGq&algo_pvid=77bddd5c-6ae2-4082-8837-73945f792fae&algo_expid=77bddd5c-6ae2-4082-8837-73945f792fae-0&btsid=0bb0622f16000865130548256e846c&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ AliExpress Frequency Counter] - Very inexpensive | ||
* [https://github.com/TheHWcave/PIC-freq.counter-modification/ PIC-freq.counter-modification] | * [https://github.com/TheHWcave/PIC-freq.counter-modification/ PIC-freq.counter-modification] | ||
| − | * | + | * |
== Built into case == | == Built into case == | ||
Revision as of 14:06, 1 November 2020
Contents
Features
- Original Design by DL4YHF
- Frequency range: 1 Hz-50 MHz
- Crystal Test Range: 4 MHz-48 MHz
- Mods to replace crystal checker with sensitive pre-amp
- PCB size：8*5.3cm
- Fits in 100 x 60 x 25 mm enclosure
- Source - AliExpress Frequency Counter - Very inexpensive
- PIC-freq.counter-modification
Built into case
- P-Touch white on black labels
- 100x60x25mm Black Plastic Electronic Project Box Enclosure Instrument Case - Inexpensive plastic case
- Plastic Waterproof Cover Electronic Project Instrument Enclosure DIY Box Case Junction Box Housing 100 x 60 x 25 mm Black
- 7-9V in
- Right angle header pins pointing to inside of card
- 4-40 x 3/16” Machine Screws
- 4-40 Standoffs
Rework - Add Pre-Amp
- Re-uses extra HF transistor that would have been used by crystal tester oscillator
- AC coupled input
- Based on
Pre-Amp schematic
When building kit, do not install
Cuts/Jumpers
- Four cuts
- Blue = 1 front side cut
- Green = 3 back side cuts
- Jumpers Red
- Green = Back side cuts
- Short etch on one cut
- Details of preamp input pin
- With parts
- Wire on back
Testing
- 4.9152 MHz crystal oscillator
- Scope frequency counter shows 4.19520 MHz
- Freq Counter displays 4.9747 MHz
- Difference = 500 Hz or 0.1% accuracy
- Can only adjust the variable capacitor in narrow range
- Freq = 25,000 MHz - measured = 24.997 MHz
- Error = 3 KHz / 25,000 KHz = 0.012%
- Freq = 10.000 Hz - measured = 9.999 Hz = .01% error
Fixing the frequency error
- Replaced 22 pF cap with 2 series 33 pF caps
- Far right near variable cap
- Added 22 pF to back of board
- Upper mid right
- Why was this an error?
- Perhaps the variable cap is too small for proper loading of the crystal
- Could possible parallel a 10 pF cap with the variable cap?
Firmware Mods
Reviews / Builds
