Delta Pulse - Take 2

[kt315]

i did look on pcb of Mustang... sniffer... he uses HEF4538B, 15V supply max.

[Emersonpaz]

I hadn't noticed. Thanks for the feedback Eduardo, according to the datasheet 74HC4538 input voltage 2V to 6V while the CD4538 3V to 18V. 74HC4538 is receiving a voltage of 10.23v do you think it won't last long? I remember seeing more users here on the forum using the 74HC4538 on the Delta pulse if I'm not mistaken.

[eduardo1979]

Just by exchanging the CD4538BE ci's for the MM74HC4538N, the T4 and T5 times went from 15us to 28us. a compromise for field research of coins and large items

You have to be careful with that, because the 74HC4538N supports the maximum supply voltage of 6V and Delta Pulse works at 12V or more.

[Emersonpaz]

Just by exchanging the CD4538BE ci's for the MM74HC4538N, the T4 and T5 times went from 15us to 28us. a compromise for field research of coins and large items

[kt315]

this trouble was i did meet. a buyer sent me the board unworking. i found a cause was CD4538's. seems there is 4538 type unworking with general RC circuit.

[Emersonpaz]

Yes, I'm using the CD4538BE, I'll try to get other ci's to test. Thank you kt315.

[kt315]

again strange working 4538. change them on another type.

in BOM file you must see a line

DD1 4538 HEF4538BP, 74HC4538N, MC14538BCP
do not use CD4538 (RCA)

[Emersonpaz]

I have all the original values of C4,C5,C6-1.5nf R7-15k, R8-27k and R9-68k and I am reading on the oscilloscope T4 and T5 15us and it should be 45us. can anybody help me?

[kt315]

GUYS,

I GIVE AN ACCESS TO THE ARCHIVE HANDY. IF SEE A REQUEST. I DO NOT SIT NEAR PC WHOLE DAY. BE PATIENCE AND WAIT.
ESPECCIALY IF YOUR SUN IS VERY HOT THERE.

[kt315]

I took the data from the forum... but i do not recommend to do this changes on your first step because headache.
get 'classic' DP, check it in a field, after 1 year of the hunting you can mod something.
i had got huge stream of laments on very unstable work on the ground from guys doing those mods. could help them nothing.
if you want to get PI working with small coils look on a side of HH, Bara, Minipulse etc projects.

small coil is just for checking/tuning in your room. you can NOT check 1x1 meter coil in VERY hard conditions of your home/house.

pleasure

[arthur1974]

Hi,
In the BOM I read the following information:

If you want to use Delta Pulse with just small coil.
Q: How small is small? D < 25 cm?

You can tune FIRST DELAY to its minimal value 12-15us.
Change C4 to 820-910pF. R7 to 7.5k.
Change C5 to 1nF to decrease STROBES' WIDTH to 20-25us.
Q:
FIRST DELAY: change C4 + R7?
STROBES WIDTH: C5?

Tune frequency to 300pps. Change C1 to 10nF and R1 to 160-180k.
Q: For small coils must ALL (C1, C4, C5, R1 R7) the above changes be made?

Thanks, Arthur!

[kt315]

good reading Chinese toys - Geotech Forums (geotech1.com)

[arthur1974]

OK, I'll leave out the sockets, have to check the sound videos on YT from KT315. I'm going to buy an OP AMP tester, which is actually still missing from my workshop equipment. I don't have a hot air soldering station, but I do have a good soldering station from Weller and solder with a low solidus temperature. Many thanks for all the good advices!

[kt315]

opamp comparator tester - Geotech Forums (geotech1.com)

User Profile - Geotech Forums (geotech1.com)

UPD. second link is not working, a bug of the forum. try

[MDfanatic]

Why would you buy electronics from eBay?

Unless you want to play Russian roulette with your money, time and patience.

Just buy from LCSC.com and you will not need to test anything.