LDC1000EVM for coin identification in coin shoot

What is your maximum allowed sample interval? There are a few parameters which change the sample rate - first, the sensor frequency affects the interval - the higher the frequency the faster the measurement time.

Also, the response time setting will change the measurement interval; although the trade-off is that the measurement resolution is decreased. The response time can be set from 192, 384,768,.., 6144 (each step is 2x the last step). In the GUI, this can be set on the configuration tab - it is the 3 small rectangle -gray/green/red next to the red sinewave on the top left). Look for the LDC Configuration: Response Time pull down selection.

Identification of metal is based off of both the RP (proximity) and L measurements; note that both of these change with frequency, so measurement at a few frequencies will improve the identification accuracy.

thank you for your reply we at the time we want to start sampling we want it to sample for about 300 milliseconds or so.  we are hoping this can be done in such a way where we can replace our current coin shoot so we are trying to shy away from using 3 different LC tanks and 3 different LDC1000's.  i did change the response time to 6144.  as of right now with the LC tank that the LDC1000EVM came with doesn't seem to cut it.  Does this sound like a lost cause or would u suggest a new coil? any other ideas

Hi,.

Are you trying to identify different type of coins? How many types do you need to identify?

Don

yes the idea is to replace our current method of identifying coins.  we of course need the US coins and coins for customers all over the world..  as of right now our program has to be tweeked a little for any new customer who has a type of coin we havent worked with before however we are always able to get there set of coins working.  We have a free fall coin discriminator at the moment using 3 inductive sensors.  this does work well but we would like to drive down the coast.  for any giver country theres usually no more then 5 or 6 coins they need to be accepted. 

Hi Robert,

To detect different metal type, LDC1000 needs to work at very low LC tank frequency. 10KHz is recommended. You can use a ferrite core inductor some 10mH. The diameter of the coil should be smaller than the smallest coin to be detected, and the distance between the coin and the coil need to be small (~0.5mm) and consistant. Oscillating at such a low frequency required a sample window of 100ms or so, therefore the coin needs to be over the coil for at least that long.

Hope this will be helpful!

Don

Hi Don and Robert,
we got a couple of EVM kits and we are trying to identify the different UK coins for a donation box.

1. any guidelines as the ideal inductance and capacitance which work best?

2. we are trying to keep the coil diameter as small as possible but the inductors we fund have a T section, i.e. a cap at the top which might affect the shape of the field? Do you have any off-the-shelf parts you could recommend?

Many thanks
Riccardo

Hi Rick,

Ideally, a large coil should be used (L>10mH) to be able to distinguish between ferritic and non-ferritic metals. But is you can only small coils, then you can still distinguish metal by their resistivity. A small, capped inducts can still work if the distance is close. The frequency should be as high as possible in this case so that the LC tank Q is higher. Because there are many types of inductors, you may need to get several with typical form factors and try them out.

Best regards,

Don

Hi Don,
I replied to your post twice over 2 weeks ago with a couple of questions and the delay is seriously jeopardising a large project. Could you kindly reply.
Many thanks
Best regards
Riccardo

Hi Ricardo,

Sorry for the confusion. Let me explain:

To differentiate ferritic and non-ferritic metals, very low frequency must be used. However, this requires large inductance of the coil, and the size will also be large because of that.

Many types of metals can still be identified regardless of their magnetic permeability. In those cases, high frequency can be used, and the coil size can be made small

Don