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Modded the Centech 97245 detector as follows:
1. Moved the ground end of the LED to the output of the 2N7000 FET - Originally the LED was lit when ever the power was on AKA a Flashlight. This mod makes the LED a signal strength indicator and a threshold setting indicator as it is only on when threshold is set too sensitive or a target is detected.
2. Doubled the piezo limit resistor to 150 ohms - reduces power consumption and makes the piezo more bearable.
3. Added a pager vibrator motor and a 180 ohm limit resistor in series. Provides tactile feedback and silent operation around others.
4. Installed a DPDT select switch controlling 'Vibrate' or 'Audible' indication of detection.
5. Installed a 100 ohm thermistor to help with stability.
6. Installed a .22uf cap to filter out ripple on the comparator input.
7. Reset internal range pot in the Sensitivity control part of the circuit to allow proper range of the external Sensitivity pot.
8. Replaced the TL062 dual op amp with a TL082 dual op amp. Improved stability.
The detector now gives varying audio tone going low when a target is detected and target detection is always accompanied with brilliant LED light. The light is a great help in presetting threshold for more depth as you can set for very low illumination of the LED in the idle state.
Note: The original board comes etched, drilled, and marked for most of these component changes but they were left out in manufacture presumably to cut cost.
The jury is still out on the sliding ring trick originally posted elsewhere in the Tech Forum. I think it works on detectors that have not been optimized with mods. It does this by mechanically bringing the detector closer to its sensitivity threshold. The sliding ring may have a benefit in reshaping the field around the ferrite rod but I have not yet been able to prove this to be true. If it does then it may still be worthwhile.
Detection distance of this detector on a 1/4" X 1/4" piece of aluminum can is now 0.75". US Nickle is 2.375"
The most sensitive area of the search probe is the first 1.5" from the tip.
This modified pinpointer really speeds up target recovery.
Dan
1. Moved the ground end of the LED to the output of the 2N7000 FET - Originally the LED was lit when ever the power was on AKA a Flashlight. This mod makes the LED a signal strength indicator and a threshold setting indicator as it is only on when threshold is set too sensitive or a target is detected.
2. Doubled the piezo limit resistor to 150 ohms - reduces power consumption and makes the piezo more bearable.
3. Added a pager vibrator motor and a 180 ohm limit resistor in series. Provides tactile feedback and silent operation around others.
4. Installed a DPDT select switch controlling 'Vibrate' or 'Audible' indication of detection.
5. Installed a 100 ohm thermistor to help with stability.
6. Installed a .22uf cap to filter out ripple on the comparator input.
7. Reset internal range pot in the Sensitivity control part of the circuit to allow proper range of the external Sensitivity pot.
8. Replaced the TL062 dual op amp with a TL082 dual op amp. Improved stability.
The detector now gives varying audio tone going low when a target is detected and target detection is always accompanied with brilliant LED light. The light is a great help in presetting threshold for more depth as you can set for very low illumination of the LED in the idle state.
Note: The original board comes etched, drilled, and marked for most of these component changes but they were left out in manufacture presumably to cut cost.
The jury is still out on the sliding ring trick originally posted elsewhere in the Tech Forum. I think it works on detectors that have not been optimized with mods. It does this by mechanically bringing the detector closer to its sensitivity threshold. The sliding ring may have a benefit in reshaping the field around the ferrite rod but I have not yet been able to prove this to be true. If it does then it may still be worthwhile.
Detection distance of this detector on a 1/4" X 1/4" piece of aluminum can is now 0.75". US Nickle is 2.375"
The most sensitive area of the search probe is the first 1.5" from the tip.
This modified pinpointer really speeds up target recovery.
Dan