Programmable TELRAD Style Finder Scope

thingiverse

#Programmable TELRAD Finder Scope# A Telrad is a type of collimating reflector sight used as a viewfinder for telescopes and other optical equipment. This is a modified, low cost Telrad design with a programmable reticle which can overlay shapes and text onto the viewfinder. Instead of a glass lens, it uses a credit card sized Fresnel lens as a collimator. Mounts are compatible with [claus57's weaver/picatinny rail mounts](https://www.thingiverse.com/thing:3125380) as opposed to proprietary telescope mounts, allowing it to be mounted to anything with a rail or [rail adapter](https://www.thingiverse.com/search?q=telescope+rail+adapter&type=things&sort=relevant). ##Materials## * Arduino Nano and Mini USB Cable * 1.8" 128x160 TFT Display Module (Model has SD and Display pins on the same size as seen [here](https://www.ecrater.com.au/p/22842092/18-inch-serial-spi-tft-lcd?gps=1&id=115931170339&keywords=&gclid=EAIaIQobChMIlISkk9Gj6gIVwworCh1ACwhcEAkYEyABEgKYR_D_BwE)) * Credit Card Fresnel Lens (85mm focal length. Available from [ebay](https://www.ebay.com.au/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=credit+card+fresnel+lens&_sacat=0)) * 50mm Square Mirror (Can usually be purchased from craft shops as mosaic tiles) * 2mm Clear Plastic Sheet (Typically acrylic) * 3 X M3 Lock-Nuts * 2 X M3 15mm Bolts * M3 25mm Bolt * 9 X M2.5 8mm Self Tapping Screws * SPST Mini Switch * Hookup Wires * 9V Battery Terminal Clip * Printed Parts ##Tools## * Rotary Tool/Dremel With Cutting Disk * Screwdriver ##Assembly## 1. Use the rotary tool to cut the lens down to a 50mm by 36mm rectangle, keeping the rings of the Fresnel lens concentric with the centre of the lens. 2. Use the rotary tool to Cut the clear plastic into a 56mm by 50mm rectangle. 3. Use the lock nuts to fix the 15mm bolts through the top 2 holes and 25mm bolt through the bottom hole of the body. They should be loose enough to allow the bolts to turn but tight enough to prevent them from sliding in and out of the assembly. 4. Screw the bolts into the mirror clamps. The holes on the clamps should be tight enough to engage the bolt thread and the mirror clamps should be able to travel back and forth as the bolts are turned. 5. Thread the wires of the 9V battery clip through the hole at the bottom of the battery well and pull them through. 6. Connect the Arduino, Display, Switch and Battery according to the wiring diagram. The wires to the 9V battery will need to be threaded through the mounting holes in the display and soldered into the battery clip leads, switch and hookup wire. Wires to the switch need to be threaded through the hole in the back panel before being soldered to the switch terminals. 7. Screw the switch onto the back panel. 8. Place the Display and Arduino into the body. The terminals of the display should be on the side closest to you. The Mini USB port of the Arduino Nano should line up with its hole in the side of the body. 9. Place the mirror between the top and bottom clamps and adjust until tight. The mirror should be held securely against the angled surface of the battery well. 10. Place the Fresnel lens into the slot parallel to the top surface of the enclosure. 11. Place the clear plastic sheet into the viewfinder. 12. Align the Arduino mount with the Arduino Nano and screw the cover onto the body. The Arduino should be held firmly in place and the USB port should be accessible from the side of the body. 13. Upload your code to the Arduino. Insert a 9V battery and switch your programmable Telrad on. The reticle should be visible in low light. Make fine adjustments to the reticle focus/position using the bolts on the front panel and large adjustments to the reticle position/layout by modifying the code. Simple reticle code is provided below. ##Code## This example code compiles on Arduino 1.8.10: #include <Adafruit_GFX.h> #include <Adafruit_ST7735.h> #include <SPI.h> #define TFT_CS 10 #define TFT_RST 9 #define TFT_DC 8 #define TFT_SCLK 13 #define TFT_MOSI 11 int w; int h; int cw; int ch; int ow; int oh; int rr; Adafruit_ST7735 tft = Adafruit_ST7735(TFT_CS, TFT_DC, TFT_RST); void setup(void) { tft.initR(INITR_BLACKTAB); //Initialise display. tft.setRotation(3); //Rotate display to compensate for reflection. tft.fillScreen(ST7735_BLACK); w=tft.width(); //Display width (pixels). h=tft.height(); //Display height (pixels). ow=-20; //Offset width (pixlels). Edit this value to adjust horizontal offset. oh=0; //Offset height (pixels). Edit this value to adjust vertical offset. cw=w/2+ow; //Centre of width (pixels). Calculate centre of width and align. ch=h/2+oh; //Centre of height (pixels). Calculate centre of height and align. rr=200; //Time between refresh (ms). Edit to change refresh rate. } void loop() { // Draw reticle here using the Adafruit display library https://learn.adafruit.com/adafruit-gfx-graphics-library. tft.drawLine(cw, ch, cw, h, ST7735_RED); tft.drawCircle(cw, ch, 10, ST7735_RED); tft.drawCircle(cw, ch, 20, ST7735_RED); delay(rr); //Refresh display to update any changes made. }