Difference between revisions of "Frequency Counter"
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* [https://www.ebay.com/itm/USA-12-PCS-5-5-MMX-2-1-MM-CHASSIS-PANEL-MOUNT-FEMALE-POWER-JACK-SOCKETS-NEW/264838025913?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 5.1mm Chassis mount power connector] | * [https://www.ebay.com/itm/USA-12-PCS-5-5-MMX-2-1-MM-CHASSIS-PANEL-MOUNT-FEMALE-POWER-JACK-SOCKETS-NEW/264838025913?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649 5.1mm Chassis mount power connector] | ||
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* 4-40 x 3/16” Machine Screws | * 4-40 x 3/16” Machine Screws | ||
* 4-40 Standoffs | * 4-40 Standoffs | ||
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| + | * [https://www.aliexpress.com/item/32833340145.html?spm=a2g0o.productlist.0.0.68406390LYz5Rw&algo_pvid=0bbf736e-a88e-4ac7-9adc-03df1259669a&algo_expid=0bbf736e-a88e-4ac7-9adc-03df1259669a-0&btsid=0bb0622a16017274930362968ef528&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ BNC connector - female chassis mount] | ||
[[File:FreqCounter-Case-11-720px.jpg]] | [[File:FreqCounter-Case-11-720px.jpg]] | ||
Revision as of 14:10, 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
- PIC-freq.counter-modification
- PCB size：8*5.3cm
- Fits in 100 x 60 x 25 mm enclosure
- Source - AliExpress Frequency Counter - Very inexpensive
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
